The best game on its system. The best of its kind. The best this era. The Best Game Ever. While the sound bites rolled on, once the dust had settled on the hype train of the original Halo, we were undoubtedly left with a title that changed perception for genre and generation. Few games inspire such devotion upon the mere mention of a name - Master Chief, Cortana, Keyes - or the label attached to any one of its hallowed multiplayer arenas. Players partook. Catchphrases coined. Stories swapped. Memories immortalized. In the eyes of most, ten out of ten.

Halo was not, however, a flawless masterpiece; early illusions of roving exploration and open terrain combat degenerating to disappointingly linear corridor shooting with unfortunate frequency. Twinned with this, the move from initially intelligent and entertaining aliens to the now infamous parasitic hordes bound within installation zero-four. And augmenting both was the game's twisted subversion in making the player battle through previously traversed terrain at its tail end, albeit in reverse. Moreover, the lack of Xbox Live multiplayer denied what many desired straight from the off: a reason to buy into Microsoft's networked vision; that undeniable online killer app.

Recognition of these flaws is important - they provide a starting point for the sequel, for justification of peerless propaganda and laudable hype. Paradoxically, it is the way in which Bungie have exceeded addressing some of these issues, only to take steps backwards in others, which prove the ultimate barometer, both for the franchise, and development of the console on which the Halo brand is iconic.

In Halo 2, the centre of this iconicity - the ring world Halo of the first game - is a distant memory. Its heroic survivor, the Master Chief, has fought his way back, a trillion miles across the void, to protect the dearest prize of all. Earth. When we rejoin the series' narrative, however, it is not with the Spartan we find ourselves - or even on humanity's home world at all - but looking upon the fragmented floating ruins of his greatest victory, Halo itself. And floating alongside it, in the first of many of the game's nods to sci-fi lore, is the Deathstar-like Covenant Holy City, High Charity.

This intro is designed to hint at the over-arching narrative sway of Halo 2 that expands on the Halo myth, lending depth to both human and Covenant perspectives of its inter-stellar war. When the initial movie ends we have begun to understand the motivations which drive the Covenant hierarchy and the effects of failure on its warrior civilization, all before we join our central protagonist in conversely high spirits on Earth Defence Platform Cairo.

The contrast of viewpoints here will play out over the course of the game, evolving to form as compelling a plot as ever seen in the genre, and demonstrating the developers' drive to fuse sophisticated story arcs to the series' signature shooting mechanic. Though somewhat underused, the fact that it ups the ante from the original is unquestionable, spinning a yarn encompassing Halo's happenings and weaving them through the framework of Covenant prophecies and religion. In Halo, you understood what was happening, and how you could combat it. In Halo 2, you uncover why; the mystery of the rings and the fate of the Forerunners. This adds scale to proceedings, consequence to conflicts, movement between cause and effect of both human and alien actions, and creates a wide array of arenas in which to do battle.

That also means a hell of a lot of action. Indeed, a sense of scale has been carried across from story to setting, heightening Halo's hectic battles on all manner of new terrain. Initial levels, from defence of the orbiting space cannon on which we first take charge of the 'Chief, to battling on the planet surface, really do capture the feel of their locales. Heated fire-fights occur in space station engine rooms and ranged gunplay turns to all-out warfare on the beaches, buildings and city streets of planet Earth.

Later on, urban warfare is swapped for the mystique and natural beauty of a second Halo ring and more besides, altering scope and battle tactics of both enemies and allied troops and casting perception across time and space to wreak havoc wherever plausible. With Halo 2, then, more than ever before, we actually feel like the pivotal player in a war of epic proportions.

A big factor in this is balance of design, both in level architecture and tools on offer to overcome each obstacle. Increased emphasis on the vertical plain is apparent upon encountering new Covenant flying Yanme'e infantry and more run-ins with Phantom warships. Level design, meanwhile, consistently throws up instances of being pinned down by lofty, unseen enemy snipers. Again, the realization of life on the battlefield wrought by Halo 2 is both gritty and satisfying; challenges overcome in the sandbox of battle giving a pleasing feeling of achievement.

Essentially the game hasn't changed. It's still Halo.

Such a feeling is only increased by using your enemies' own ideas against him. Raise a wry smile as you boot a foe out of his charging Ghost with a timely press of the X button. Bask in your own brilliance as you double back upon a cowering Elite ducking for cover, awaiting the return of his precious energy shield. And revel in your own smugness as you fell a foe, only to turn his dropped weapon on his counterparts with Halo 2's new dual wielding function, holding Y to add his automatic to your own human variant and mowing down all who stand before you.

These improved in-battle options are helped out no end by some much-needed and well handled weapon balancing. Gone are the assault rifle and pistol as generic artillery, replaced instead by the SMG and battle rifle that evolve the original's basic firearm partnership. The shotgun is still present; less effective from distance, but deadlier from point blank range, and melee attack does less damage than before, but includes a handy dash function that homes in on opponents in the player's firing line. The rocket launcher too is improved, retaining its power and gaining a handy lock-on function.

Aside from these however, are new offerings that level the playing field. The beam rifle, for instance, is ostensibly a Covenant sniper rifle, and provides an avenue of attack and abundance of sources that the solitary human sniper of the first game could never approach. Likewise, the brute shot and fuel rod gun both offer explosive counterpunches to the human rocket launcher, that can just as easily be appropriated for the players own use. Then of course we have the Energy Sword, an impressive and deadly one-hit-kill melee weapon with limited charge, but devastating effect.

The upshot of all this is an unheard-of level of customization available to individual players style of play; both with two primary weapons and favoured dual wields. This makes Halo 2's gunplay a deeper, more strategic evolution of the first title's form; the impact of which on the campaign mode cannot be understated, especially in Co-Operative, where such personality only compliments the mode's teamwork ethic. Rarely can a combination not be made that will suit two players, especially when vehicles of both human and Covenant origin are also to be considered.

So far then, all seems rosy. Yet, despite these many improvements, it is only upon extended play that several of the games biggest clichès begin to reveal themselves.

The first of these is also the least initially apparent, and the most indicative of a lack of evolution in terms of overall game structure from the original. In a word, it can be called linearity, though in truth it applies more to over-reliance in later, plot-heavy stages to drive the action along by this more truncated means. While proceedings rarely degenerate to the lows of Halo's linear corridor blasting, they do degenerate earlier, creating the sense of less freedom and a dearth of ways to approach later scenarios; ironic, given the added options potentially afforded by the new weapons.

Coupled with this is the confusing design of many of these later levels; Covenant and Forerunner-built architecture carry the same colours and hues on their many identical walls, with very few identifying marks, imbuing a feeling of disorientation.

Dual wielding is a great addition, although you lose your ability to throw grenades.

If interior design is often annoying, however, it is nothing when compared to the disappointment embodied by the vast majority of outdoor areas on the second Halo ring, and their own linear nature. That there is no equivalent to the original's self-titled first level, Halo, or the roving snowy plains that made up the battlefield for many of the first adventure's closing scenes, is frustrating. That they have been replaced by the confusingly choreographed corridor control mentioned above is enough to disillusion the series hardcore following, for whom these levels embodied the true spirit of the game.

The true disillusionment however, is saved for the very ending; or more precisely, the lack of one. For no sooner has the story and action truly reached the edge of inspiration when it cuts out without the faintest of warnings, leaving no feeling other than an empty one of none-accomplishment. The big finish of the original Halo may be a memory in the ongoing narrative of the series, but the fundamental discourse laid down by it and its genre forebears still rings loud in the mind. For Bungie to leave us at the finish of a console generation's most awaited game with an ending that amounts to "To Be Continued" just feels like a cop-out.

Other flaws are more minor, but also stand against that which we have come to expect. New vehicles are criminally underused, while other more familiar armored beasts are utilized often only in areas offering very little choice in the matter. This extends also to the Banshee, which many thought could potentially bypass entire sections on the player's whim, or find alternate points of entry for more open ended, objective-based gameplay. Instead, the craft has once again been ushered into the occasional aerial dogfight.

The opening is pretty uninspiring, but things become a lot more interesting..

Even a giant Starship Troopers style robotic scarab promises much use, only to offer very little. This, perhaps, as the biggest of all mechanical assistance in the game, can also be considered this facet's compounding factor, though for Halo diehards, an irritant as simple as overtly noticeable texture pop-in throughout the game will be just as indicative. Many may feel let down, be it due to reaction against the hype or just from holding unachievable elevated expectations, but plenty of this will be justified.

To discount Halo 2 as a great game on these grounds, however, would be foolish, not least because Campaign is only half of what it has to offer. For not only does Halo 2 include the same split-screen and system-link options that attracted the original so many fans, but it now, finally, comes complete with ready-made online play. And what a playground it is.

Attempting something new in online shooters, Bungie have made the interface as simple to navigate as possible. Logging onto your gamertag, quick button presses can bring up friends lists, from where text or recorded voice messages can be sent. Swift menu selections can easily find players joining other random contestants for ranked or unranked variants of classic Halo gametypes. Custom teams and modes can also be created, clan matches set up, and entire teams taken across between gametypes to be matched against other teams of similar ability.

Of course, in early stages of an online title there will always be flaws; the inability to search for certain gametypes and choose a selection from a produced list is a rather large omission. As too, is the inability to carry a custom party of more than one person over into the Rumble Pit mode for some free-for-all Slayer, making it currently almost impossible to play ranked deathmatches in a team incorporating a mixture of friends and randoms. These however, are at least partially forgivable when considered against the ease with which the service is used, and the wealth of options currently offered. Moreover, Bungie's own homepage makes things more accessible still, allowing players to track their own rankings via gamertag and clan names.

The energy sword proves to be a deadly weapon.

These options though, however impressive, pale in comparison to actually playing the game online. New multiplayer maps, for the most part, replace the old Halo cast of arenas, with the few remaining ones having been given obvious facelifts. In all cases, it is clear that the up most effort has been made to tailor the game to its online mode, keeping a steady framerate and connection without sacrificing aesthetic values.

Never is this clearer than when a pinpoint sniper bullet splits your target's skull in a frantic eight-player free-for all, operating with four people on your home machine. The most pleasing aspect however, is how natural this occurrence is made to feel. Indeed, the extent of the service's optimization can be felt on even the most basic connection; our own standard 128k upload, running through a router on four-way split, healthily accommodates two players on one Xbox playing with six other people online.

Remnants from the Campaign mode also start to find fruit in Halo 2's online mode, with the true genius of its new weapon balancing becoming instantly and obviously apparent. Level design, too, retains the focus on the vertical, with certain maps offering as tactical and deep an example of the genre as found anywhere on PC or console. Voice communication too, is a standard setter; providing the perfect means for relaying tactics, or even (cruelly) gaining an enemies attention, only to lure them to their doom at the butt of your smoking shotgun, with Halo 2's soon-to-be-imitated Proximity Voice.

Consider too that the online infrastructure is primed for regular level downloads, and we may well yet see new variants of some classic Halo deathmatch arenas appear for download on Live, as well as improved matchmaking options and brand new maps. Consider also that Bungie is just the developer to take advantage of such an opportunity; their passion and commitment have already produced the standout online title of a console generation. Make no mistake, FPS fans: this is the game to sell Xbox Live.

And the thought of Xbox Live should, in turn, sell Halo 2, alongside the campaign mode. Those without Live, however, should still take heart; this is a game that, despite falling short of unfathomably high expectations, can still claim to be in the upper echelons of the year's triple-A titles.

Production values are never less than astounding throughout - from jaw dropping lighting to majestic character models, and vastly improved cinematic direction which effortlessly portrays the enjoyable screenplay. Sound too, is of the highest calibre; high quality voice talent used to bring life to humans, Covenant and more besides, backed up by a musical score that bounds between epic and pleasantly surprising. We defy anyone not to raise a smile when, in the heat of a pitched battle, sound will turn from loud organ music to a quaint little melody more reminiscent of wandering around the world of Albion in Fable, than fighting for your life on an artificial planet in deepest space.

And there are other considerable positives too. What was possibly the biggest flaw of the original Halo is answered here; The Flood are present, but their role downplayed and their intelligence upped to increase their entertainment value. Generally speaking, the entertainment offered even in Halo 2's most linear areas is arguably preferable to revisiting old areas in order to fight your way back out. Again, another major criticism of the original; again, another flaw addressed.

In truth then, for everything Halo 2's campaign does wrong, there are aspects which go above the vision of the original. The requisite AI is here, upped to new levels and thrust upon a new string of foes who add both to gameplay and story as a whole. It can also boast an improved weapon set, sophisticated urban level design and a greater sense of scale than ever before. Visually, aurally and cinematically, Halo 2 is a breathtaking experience, and - ending aside - is deserving of its place as one of the best games its system will ever play host to.

Unfortunately, however, Halo 2 just doesn't deliver enough to top the importance of the original. That's not to say it is not a more complete package, or even, arguably, a better game. But it is by no means the definitive first person shooter of its generation that we were promised, and that disappointment weighs heavy. The emotion induced by the core campaign mode is simply a more stunted form of that which revolutionized the genre three years ago; a familiarity that breeds no contempt, but nonetheless fails to fire the spirit to such potent degrees.

This however, is juxtaposed against the towering technical achievement that is Halo 2's online multiplayer. It is a truly staggering addition to an already impressive production which skirts any doubts as to the viability of The Master Chief as a gaming figurehead, and Xbox as a brand synonymous with such classic games.

Ultimately, with Halo 2, we are not faced with the best game ever; possibly not even the unequivocal game of the year that its forebear undoubtedly was. However, its ability to do credit to its own lineage is also worthy of the renown in which many hold the Halo name. "Earth Will Never Be the Same Again", said the trailer. "Work Won't Matter Anymore", said the ads. And in the world of videogaming, that Halo 2 can hold its own post-hype credentials high enough to do these statements justice, is praise enough.