Open world full of shooting, but also glitches and bugs.
Story starts in August 2010 in Venezuela. A mercenary approaches to a businessman called Ramon Solano and he asks the merc to rescue a Venezuelan Army General named Carmona. Your chosen merc does what he or she is told, but after a successful job Solano tries to murder you without paying. Luckily you manage to escape and start planning revenge against Solano. Story moves forward with occasional cutscenes, but it's not the story that pushes you forward in Mercenaries 2: it's the destructible environments and explosions.
Graphics are average, but at least colorful and since this game is big texture popping happens all the time. At times it's so bad that a whole tank can appear from thin air right in front of you. Glitches can be seen way too often and it's clear that Mercenaries 2 should have needed more time in development. You will also notice that the time of day never changes: it's always around noon in Venezuela. Explosions happen all the time and they are the highlight of this game: it never gets old. Almost everything can be destroyed so how much you enjoy playing Mercs 2 depends on how much you enjoy blowing things up.
Sound design and music are functional, but not that remarkable either. Only occasional problem is that AI characters sometimes repeat that same line of dialog over and over again. It gets annoying fast, but if that should happen you can always shoot him.
Gameplay starts by choosing one of three mercenaries from the original game, all of which have their own appearance and voice acting. Jennifer Mui is the fastest, Mattias Nilsson has fastest regenerating health and Chris Jacobs has most ammo to use. All characters follow the same storyline that centers on your character of choice. This is a third person action game, but since all the action happens outdoors the camera is never a problem. This is a rare achievement in this genre of games.
Controls are good and much better than in GTAIV in my opinion. Shooting is easy and most importantly satisfying. Vehicles are fun to steer and there are a lot of them. Causing havoc by using air and artillery strikes is always a pleasure to perform. Just remember that you can't shoot everybody: every time you kill a civilian you will lose money. So have fun, but not mindless fun.
Structure is the same as in any other open world game. You have a big open map to explore and you travel to different locations to get missions and side quests. You get to do business with lot of different sides of the same conflict and it will bring at least some variety to the overall repetitive missions: go there, kill this, blow that structure up and come back.
Enemy AI is almost non-existent: they fail to react even if you shoot at them, they shoot each other, commit stupid suicides and so on. For me this wasn't a huge problem, since I was already too busy in shooting them than paying attention on what they were doing besides shooting back at me.
What can really test your patience is the save system: there are occasional checkpoints between different stages of a mission, but usually if you die, you end up doing those same things over again from the beginning. Luckily there's one feature that makes Mercenaries 2 a lot easier to handle: online co-op with a friend. At times it seems that this game was meant to be played in co-op, because it makes an average shooter exponentially better.
In the end I personally enjoyed Mercenaries 2 a lot more than I did GTAIV or Saints Row. Frequent bugs, glitches and an abysmal enemy AI drop points quite substantially, but if you enjoy blowing things up I recommend you to check this game out.