If GTA 4 is a skinny decaf latte then Mercenaries 2: World in Flames is a double shot full fat Americano with a can of Red Bull on the side just in case. Though both are of the same video game genre, the differences between the two are undeniable. Where GTA 4's Liberty City is a more mature, realistic open world with an underbelly of subtle, satirical humour, Mercs 2's Venezuela is an adolescent, over the top open world with slap you in the face frat house laughs.

Think comparisons with GTA 4 in the opening paragraph of a Mercenaries 2 preview are unfair? Well they aren't. GTA 4 is unshakable in its domination of the genre, and any upcoming open world action game, be it Mercs 2, Just Cause 2 or Saints Row 2, has to endure such comparisons. This is the reality of the market, the bar has been raised, and this is something Pandemic's Cory Lewis, who spoke to us following his live presentation of the game to press at EA's recent Games label event in London, freely admits to.

That's enough of GTA 4 for now. Let's talk changes. Pandemic has increased focus on storytelling this time round, an aspect of the first game believed to be particularly weak. Set in Venezuela, South America, Mercs 2 is a revenge mission in every sense of the word. You start the game as one of three possible playable mercenaries - the same three from the first game - Mattias Nielsen, Jennifer Mui and Chris Jacobs. You've been contracted by a Venezuelan billionaire businessman called Ramon Solano (no relation to the Peruvian trumpet-playing West Ham midfielder) to free General Carmona from a military coup. The game's opening level, which acts as a simple tutorial, sees you storm into a heavily fortified building, blowing the gates open with a mini-game bomb strike and killing scores of unfortunate guards with an assault rifle and satisfyingly destructive grenade launcher. Boom.

You immediately get a sense of the game world's tenancy to collapse under the stress of your imposing weaponry. Trees crumble and fall. Grass and foliage light up in flame. Buildings and structures collapse at the merest whiff of an explosion. Pandemic's Venezuela is designed to be trampled on, blown up and generally made a mockery of by the player, and it will offer little resistance.

This is open world gaming with an emphasis on blowing stuff up

The controls are as you'd expect. Although Lewis demoed the 360 version of the game, we tried out the PS3 version afterwards, which we reckon looks just as good. R2 fires your primary weapon (L1 fires secondary), L2 crouches and R1 switches weapons. Triangle is the context sensitive interact button, mostly used for jacking vehicles. Square is for reload, circle melee and X is for jump. Clicking in the left thumb stick will make you sprint and doing the same with the right thumb stick will zoom in. And finally the Select button opens up your PDA and the game's map.

Once you've rescued Carmona a cut scene kicks in revealing Solano to be a two-faced double crosser. Rather than paying you for your plight he tries to kill you, which is obviously not cool. You escape, but not before he shoots you in the, well, ass, since Mercs 2 is an American made game. What the hell. He shoots you in the arse. We're British after all.

Solano then claims Venezuela for his own, which has absolutely nothing to do with the real Venezuelan political situation, we promise. While watching him gloat on TV, and with an extremely sore derriere, you vow to take revenge on the cheap rat. Cheating you out of your hard earned cash is one thing, putting a bullet in your bum was clearly the straw that broke the camel's back.

Lewis describes Mercs 2 as like a video game version of an over the top, tongue in cheek Jerry Bruckheimer flick. Think Bad Boys, The Rock, Con Air and Armageddon, that sort of thing. Ironically, your base of operations in the game is the previously Solano-owned mansion which you wrestle control of in an early mission. From here you're able to build up your own private military army, a new feature added for the second game. This time around there are five factions to either make friends or war with, over 130 vehicles and an 8km by 8km world to devastate. Lewis sums it up for us: "If the question is: 'Can I go do this?' the answer should be: 'yes'."

Some of the explosions in Mercs 2 are truly spectacular

A case in point: tank hijacking. Here you need to position yourself in front of the metal monstrosity, climb up the barrel and trigger a QTE mini-game. Using the thumbstick to balance yourself as you cross the barrel, you then need to press B (on the Xbox 360 pad) when prompted to open the tank hatch, A to wrestle a grenade off the driver, drop it in the tank and seal him in. You'd think that would wreak havoc with the tank's innards, but, pleasingly, it doesn't. You jump in and then it's playtime.

We're not big fans of QTE mini-games of this kind. Most of the time we can't see any good reason for their existence. It's almost as if they're in there because developers couldn't work out what to make players do to overcome a repeated challenge. But in Mercs 2 it fits. The mini-game is in keeping with the tone of the game. This is silly, accessible fun. Mercs 2 is not to be taken seriously. It's a playground for innocent fun and slapstick laughs.

The PDA mini-map in the bottom left corner is unmistakeably open world game design, with the now standard route-plotting facility. Players have an on call extraction for when the going gets tough or when you simply need a lift - an Irish helicopter pilot called Ewan will do the honours and bring you to any friendly place on the map. We play a mission given to us by the P.L.A.V. (People's Liberation Army of Venezuela), to liberate an entire area from the tyrannical civilian-killing antics of a Venezuelan army general. The idea is to draw out the skulking coward from hiding and, essentially, blow him and his cronies to kingdom come.

The mission requires you to destroy three buildings (you'll find most of your time is spent blowing up buildings in Mercs 2) which lure him out of hiding. You get wind that his forces are attacking a church which you speed towards and defend from relentless army goons. Eventually you lure the general into a soccer stadium where he has a number of civilians held hostages. Not one for subtlety, you storm in, destroying everything in sight. Unlike Solano, the P.L.A.V. pays up, allow you to use their faction base and open up some more of the map for you to explore.

We can't wait to get some hands on with the online coop

Mercenaries 2 has a lot going for it, most notably the destructible environments and seamless drop in and out online coop (which we haven't seen in action yet, so can't comment on). But there remain technical areas of concern. The frame rate issues of earlier builds have been improved but there are still moments of noticeable slowdown when things get busy and the draw distance is working overtime. The AI often suffers from complete moronic stupidity and the vehicles can be frustrating when driven in confined areas because they get stuck on bits of the environment. These are all trials and tribulations any developer of an open world game must tackle, and, given that the game isn't due out for a few months, there's still time for Pandemic to optimise, so we have hope these problems will be less noticeable when the game is finally released this September.

Mercs 2's in your face over the top blow everything up action won't be for everyone of course. The lack of a competitive multiplayer might turn away some, but the online co-op is hugely promising. Some people baulk at the ridiculousness of the Mercenaries franchise, but it's this ridiculousness that is shaping up to be the game's main draw. Some of Mercs 2's explosions are right up there with the most spectacular in gaming. Like we said at the top of the preview, if GTA 4 is a skinny decaf latte then Mercenaries 2: World in Flames is a double shot full fat Americano with a can of Red Bull saved just in case.

You might be surprised to find out that the first Mercs game was the biggest selling new IP of 2005, so there are plenty of gamers out there anxiously awaiting this sequel. From what we've seen, they won't be disappointed.

Mercenaries 2: World in Flames is due out for Xbox 360, PS3, PS2 and PC on 5 September 2008.