I've actually been planning to review this for awhile, so here goes. Again, as with my metro 2033 review, i'm gonna give you, the public, my thoughts, nothing more.
First, I wanna get my criticisms outta the way first. Just Cause 2 is literally the first game that I cared ABSOLUTELY FUCK ALL about the story. It's so thin it would probably fall apart under a light drizzle. I've played Mario games with deeper material. Second, the characters are pretty bland, their accents are borderline offensive, and the models are meh at best.
That outta the way, I just wanna say that this game improves on its predecessor in virtually every way imaginable. The island locale is simply beautiful, more than making up for the character models, and one of the biggest free roaming worlds i've ever seen. (Also, explosions look great.) You'll traverse deserts, glaciers, forests and villages with ease thanks to the kick-ass grappling hook. Gone is the grapple gun form the original, and in its place is something that provides for tons of pure, undiluted fun.
If you played Just Cause 1, you'll know you ain't in this for the story. You're here to blow shit up. And this game knows it. Free roaming is highly encouraged, as is unhindered rampage and slaughter of military personnel, highjacking vehicles, blowing up installations and fuel dumps, and more.
The grappling hook mentioned above makes traveling a breeze. A quick button press and you're flyin' towards whatever you aimed at. A tap of another, and your magic parachue bursts open, really getting you going and providing an invaluable means of transport if you don't wanna drive or fly everywhere.
The hook also provides for hilarious experimentation. At an airport, a soldier was shooting at me. Rather than simply shooting back, I used the hook to lash him to a passing jet that was taking off. The rag doll physics (also an improvement over the stiff animations of the original) worked their magic as the soldier was dragged across the tarmac, screaming in terror, before lifting off into the air with the plane, dangling from the belly like an obscene yo-yo, at which point the rope broke and the poor bastard fell to his death, forcing me to pause the game from laughter and wonder what the future will hold when a dear friend of mine comes home this summer and tries his hand at this stuff.
Gunplay and movement is solid. You can carry two one handed weapons and one two handed weapon, and upgrade your weapons and vehicles via the black market through weapon and vehicle parts you find througout the world. The black market is handy, as you can order pretty much any gun or vehicle, or request a fast travel from place to place, at any time.
But this same handy aspect bothered me at times. Rather than going down a checklist of things you would like the dealer to drop, you have to order everything individually. This isn't a problem when you want a vehicle, as you're not gonna drive two at the same time, but when i'm using a SAW as my two handed gun, and an MP5 and sawed -off as my left and right weapons, and I need more ammo, that's 3 trips to the menu. But for me, this was really just a momentary inconvenience.
All in all this game is FUN. Experimentation is encouraged, the tutorials really help ya get into the swing of things and don't waste their time on bullshit you'll only use once, and it doesen't pour nearly all of its awesomeness into the story. The main line is really short, and upon completion, you can just keep exploring, destroying and doing side missions, which I found are all extremely varied, fun, and have a high potential for hilarity. If you have a friend, and you can dig swapping turns and just watching each other, you'll have a blast. (No, there is no multiplayer, another lost bit of potential.)
I'll leave you with this. If toppling a stone statue of an island dictator, lashing his giant, now disembodied head to your helicopter, and using it as a wrecking ball against helpless people on the interstate before crashing into an overlooked over pass and perishing in a fireball of metal and rock dosen't sound fun, you really need to reconsider what you're doing with your life.