Okay, so with hindsight I guess I may have spoken a little too soon. At the end of my E3 preview for 2K's XCOM, I stated that I'd be delighted and surprised if anything else made such a successful play for my affections. Needless to say, I was proved wrong the following afternoon. Eidos Montreal's Deus Ex: Human Revolution was one of the last things I saw at this year's Expo, but somehow it managed to eclipse almost everything that came before it.

As I predicted, this rampant success was as surprising as it was delightful. The first presentation of Human Revolution had an awful lot to live up to - and not just as a result of that incredible, instantly memorable trailer. You see, the Deus Ex license is a solid gold property, a name that provokes powerful emotions among older gamers. The first entry in the series, developed by Ion Storm and released at the turn of the millennium, is still regarded by many as one of the best games of all time. Long-term fans have already had to suffer one alright-but-disappointing sequel, 2003's Invisible War; after so many years, the thought of another let-down seemed almost unbearable.

And yet somehow, the development team in Montreal appear to have shrugged off these weighty expectations. Barring a few fresh concepts and design, the new Deus Ex is immediately recognisable as the descendent of its cybernetically-enhanced ancestors. Eidos' E3 demo started off with a comparatively quiet slice of exploratory investigation before moving on to more violent, murderous pastures, but in both cases the game boasted the qualities that veteran fans know and love: rich atmosphere, the freedom of player choice and, above all else, a keen sense of intelligent design.

Set in 2027, almost three decades before the events of the original game, Human Revolution is the story of an unfortunate security officer named Adam Jensen. After the bio-mechanics firm he works for is violently attacked - by perpetrators as-yet unknown - Jensen is left looking like a bloodied shop mannequin; the head of the company steps in and has Jensen operated on, against his will. When he finally wakes up, he discovers that his body now has bionic arms, as well as whole bunch of other neat tricks (iTunes compatibility comes as standard). Our man then sets out to uncover the truth behind the attack, embroiling himself in a web of conspiracy that stretches across the world.

The demo kicked off in spectacular fashion, with a cutscene showcasing Jensen's arrival in the Chinese island metropolis of Heng Sha. Like many dystopian cities, this place has a duel-layer social split going on, with the wealthy locals literally inhabiting a higher plain of the city, far above the slums below. It's a classic sci-fi setup (or a hackneyed cliché, if you're cynical), but as with everything else here, Human Revolution has a strong flavour of its own. It looks amazing too, a riddle of stacked buildings, ridges and overpasses, decked out in a smoggy, sand-coloured palette.

Jensen's objective in the showcase was to track down a hacker he'd been following, but thanks to the Eidos demonstrator, his first act was to threaten an innocent bystander, a young Asian loitering near the docking area for flying vehicles. In first-person perspective, Jensen approaches the man and whips out his gun. The civilian reacted with immediate surprise, and as the demonstrator aimed at his face he began to babble in fearful Chinese. Even after the player turned away, the pedestrian continued to whimper and shake in his boots, arms raised in terrified supplication. I felt quite sorry for the poor chap, but Jensen was in no mood for hanging around.

The demonstrator descended a concrete staircase into the main body of the city - a busy market area full of fluorescent signs and seedy locals. While the area itself wasn't exactly packed with NPCs, it was explained that everyone here was a unique NPC who would engage with Jensen differently; if we hadn't threatened the young man, we could have chatted to him, and he'd have had something to say. Social interactions are one of the four pillars of Deus Ex's gameplay, alongside stealth, hacking and combat. All of these skills have their part to play, but Eidos Montreal state that you'll never be forced to play one way or another. If you so choose, you can even complete the game without killing a single person (although I'd wager that you might have to knock quite a few people out).

To support this freedom for the player, every major problem in the game has several solutions. For example, a few minutes into the demo Jensen needed to get into a nightclub called The Hive - a flashy joint with huge video screens filling its exterior walls. In the presentation, the demonstrator took the simplest path and simply paid to get in - but there are numerous ways to gain access. You might talk your way past the hefty bouncer, beat him up or even kill him. Alternatively you might be able to find another way into the building, either via a backdoor or a through a sewer pipe that comes into the club. Some of these entrances are more obvious than others, so it might be helpful to interview local NPCs for hints and suggestions.

The hazy interior of The Hive was just as detailed as the outside world, and contained even more characters: tough-looking punks slouching on seats, and nubile dancers strutting their stuff nearby. Jensen was looking for a man named Tong - the club owner, and suspected associate of the local Triads. After a quick chat with one of the barmen downstairs, the player proceeded to a more secluded area in the upper levels of the club, where a weathered old man was keeping watch over a second bar. This new character looked particularly ravaged by the effects of time: like Jensen, one of his arms was made entirely out of steel mechanisms, while his face was covered with strange red coloured patches, somewhere between a birthmark and a serious burn. He looked decidedly creepy, but Jensen seemed determined to find out what he could.

As with the earlier interaction with the bouncer, the conversation with the barman resulted in a shift to a cinematic third-person perspective, with the camera cutting to Jensen whilst he spoke. Like Mass Effect and its derivatives, Deus Ex uses a dialogue system based on general approaches, rather than fully spelling out what you might say. At important junctures, the D-pad is used to choose between several different angles of approach, each represented by simple one or two-word titles (although a more detailed explanation seems to pop up, if you want one). These options aren't your typical RPG fodder, either: in the case of the barman, Jensen was given the choice of "Advise", "Insist" and "Pinpoint," - each employing wildly different tactics. There was a pleasing sense of underlying psychology here, in that it genuinely felt like the player was trying to reason with and outsmart the barman. Jensen attempted to persuade the barman that it was in his interests to set up a meeting with Tong, because he had information that would benefit his organisation; the barman replied that Tong was already well aware of the hacker in question, and that his operations were too insignificant to be of interest. In short, the player appealed to his opponent's ego, and failed. Had he taken a different tactic, he might have succeeded.

Jensen finally managed to get the info he was looking for by eavesdropping on a pair of club workers who were discussing a lost PDA, then heading to the toilets to retrieve the item in question. From here he was able to gain the password for a locked door that led into the off-limits section of the building, and eventually to an air vent which allowed for some opportunistic spying. Again, this was just one of several paths the player could take; had the meeting with the barman been more successful, none of the sneaky stuff would have been required. At any rate, in the E3 demo the stealthy path won the day, leading Jensen to a warehouse area in the city harbour.

As impressive as the more thoughtful side of the game was, things really started to get showy in the second, combat-focused half of the demo. By this point Jensen had changed out of his long leather coat and into a more practical suit of body armour, exposing his metal arm and other enhancements. We got to see a lot more of these too, as during actions the camera will frequently switch to a third-person perspective - most notably while taking cover, or when sneaking in to perform a stealth takedown. The shift in viewpoint is handled very smoothly, and while it's still a touch that may upset the odd Deus Ex die-hard, these moments seem to fit the game very well - further adding to the carefully-crafted cinematic feel.

Besides, the naked truth is that the third-person bits look exceptionally cool. The non lethal takedowns are decent enough - Jensen creeps up on a guard, taps him on the shoulder and then slugs him as he turns - but when our man decides to get his claws out, that's when things get really slick. At one point the demonstrator snuck up on a guard sat typing at a desk; at the touch of a button, Jensen re-arranged his arm into a long blade, and then skewered his victim through the back of his chair. Later on, he killed two guards at once, Assassins' Creed 2 style, as he dropped down from a height. Oh, and you know that bit in the trailer where Jensen smashes through a wall and snaps the neck of someone on the other side? Well, you can do that too. By powering up one of your modifications, obscured enemies will appear as glowing outlines, mapped against the scenery. Simply line yourself up so that the wall is all that separates you and your enemy, and BAM! Bob's your uncle... a very dead uncle, with a shattered neck and a shocked look on his mushed-up face.

The stylish nature of combat extends beyond these scripted executions, too. Early on in the second half of the demo, Jensen produced a scoped crossbow and sniped an enemy from across the yard, leaving the poor bugger pinned against a packing crate. Later, he used a cloaking device to crawl under a parked vehicle and right in front of an unsuspecting trooper, who was swiftly snuffed out with a single shot from a silenced pistol. As with the more pacifistic side to the game, it seems that there's a huge amount of choice with regards to the way you approach your goals - and that's hugely exciting to me, because this freedom was one of the very things that made the original Deus Ex so wonderful.

And just to heap yet more icing on the proverbial cake, Eidos' demo finished with a short sequence that seemed designed to cram as much exciting stuff as possible into a three-minute scene. The fun started as Jensen climbed onto the roof of the warehouse and approached a glass skylight, allowing him to peer down onto a quartet of guards in the room below. Rather than taking the subtle approach, the demonstrator simply crashed through the window and dropped into the middle of the group, activating some form of body augmentation as he went. Just as the guards began to react, Jensen span in a quick circle, releasing several steel orbs. These orbs opened to reveal several more smaller spheres, which then opened in turn... and then suddenly all four of the bad guys had been wiped out in a hail of shrapnel; at this point in the presentation, I thought the man next to me was about to start crying.

It didn't end there, either. Moments later a helicopter flew over the top of the warehouse and dropped down an enormous shipping crate, which then unfolded itself to become a giant spider-mech. Jensen then duelled this beast with an RPG, demonstrating a weapon upgrade that allowed him to fire rockets from behind cover: from the looks of things you tag your target, summoning an on-screen icon distance counter, then blast away as soon as you're in a safe spot. After that Jensen finally located the office with the data he needed, only to find himself facing the lethal threat of a... actually, I'm not going to say. We can keep that last bit a surprise. Don't want to spoil all the fun now, do we?

To state the blindingly obvious, I think that Deus Ex: Human Evolution looks amazing. I know it's important not to jump the gun on these things, and Eidos Montreal clearly still has some way to go before next year's release, but I'll happily admit that I'm now utterly stoked for this game - and I say that as someone who dearly, dearly loves the original title. Aside from the new perspective, the only potential irritation I can foresee is the use of a recharging health system. I know that's the in thing these days, but the first Deus Ex gave you a different vitality score for each of your limbs. That might sound ridiculously hardcore, but it meant that you could get crippled arms, affecting your aim, or even have your legs blown off altogether. I can't say I'm that surprised that Eidos has ignored this feature in favour of a more inclusive system - the second game also scrapped it - but it's a minor shame none the less.

There are unanswered questions, too. The developers have told me that the shooting in the game is based around player skill rather than stat points, so it'll handle more like a first-person shooter than, say, Fallout 3: if you carefully aim at a foe and pull the trigger, you'll hit them. But if that's the case, how exactly do the RPG elements factor in? Eidos has also said that it'll be impossible to max out all the skillsets in one playthrough, forcing you to either specialise, or to play as a jack of all trades (and master of none). But what exactly are these skills? And how do the body augmentations work?

And then, of course, there's the biggest poser of all: Can Human Revolution match the greatness of the first Deus Ex? This is the question that pains me the most, because despite everything I've seen - or perhaps even because of what I've seen - I have some kind of internal self-defence mechanism that's kicking into gear. It won't let me see through walls, or shower people with shrapnel; it's a barrier that's designed to protect me from disappointment. If Eidos Montreal fail now it's going to hurt like hell, but every fibre of my body wants to believe that they can pull it off. Godspeed, boys.

Deus Ex: Human Revolution will be released early next year on PC, PS3 and Xbox 360.