Good Times With High Explosives.
This game is just what it claims to be, and that is not the second coming of GTA. Mercs 2 is about blowing up everything you want to with a staggering array of vehicles and weapons. If that doesn't appeal to you, and it may not, this is NOT THE GAME FOR YOU. In much the same way that you wouldn't reccomend La Pucelle Tactics to someone who loathes strategy, this is a game for mindless action.
The graphics look good, and the explosions are glorious, up to and including the nukes... yes... nukes. With a few weird exceptions like rocks, everything can be reduced to their componant molecules. There is no real attempt to tell a story, and that's fine, because this is just about being in a BIG sandbox with all the sandcasltes you want to crush. The fact that it's surprisingly entertaining for long playtimes, just goes to show that Catharsis is alive and well.
In Mercs 2, you plays as one of three characters, who, aside from player models and one unique "ability" are pretty much the same. You've been cheated, and you'll do a bunch of quests and sidequests in between bouts of self-driven mayhem. It's that simple, and as so many have said, if you want that, get this.