There's a reason Just Cause 2 is so hard to find in retail stores. The answer is pure and simple, this is quite possibly the best open world game available on the 360 to date.
Just Cause 2 has many unique things going for it, such as the style of combat and the size of the play-zone.
In the game, you are given control of "Scorpio", and all of his open weapon slots to fill to your liking. Up on the d-pad lets you wield your two-handed weapon (like an assault rifle or sniper rifle). If you press right on the d-pad once, you'll use your primary one-hand weapon, and pressing it again cycles to your secondary one-hand. Press and hold it, and you'll dual wield them. You also have a space for grenades and c-4 (or 'triggered explosives' in-game) by pressing left. One of the cooler features is your black market contact "Sloth Demon", who you can call at any time by pressing down (d-pad), then the Y button when you hear a pinging sound. He arrives in a helicopter, and from there you can purchase any gun in the game (provided you've unlocked them) and upgrade your guns with weapon parts. You can also buy and upgrade vehicles, but there isn't a wide selection available for purchase, so i'd just stick to hijacking your cars. Another problem is the cost of these "hot drops". Vehicles, weapons, and explosives are VERY expensive considering how quickly you'll go through them.
Just Cause 2 also has one of the biggest in-game worlds i've ever seen in my 12 years as a gamer. It takes nearly ten minutes (give or take depending on the plane) to fly from one side of the map to the other. The environments vary from blizzards in the mountaintops to heat waves in the desert, and from sprawling cities to open waters. Most environments are divided up amongst the huge islands, with rainforest acting to "blur the lines" so to speak. While this is great, and makes for gorgeous views and more possibilities to wreak havoc, this also quickly becomes a royal pain. Simply trying to get from one mission to another becomes a chore, and often takes longer to do than the missions themselves, but at least there's around 150 different ways to get there, the variety of vehicles is quite large.
Another problem is the A.I. You're CONSTANTLY hounded by the military police, often for the dumbest things. I remember once, I simply jumped next to the side of the road, and two seconds later there were five soldiers shooting at me. Also, the fact that they will chase you through hell and high water makes getting around all the more challenging.
But all in all, Just Cause 2 is a must-own. Gameplay is solid, sure it has a few problems, but what game doesn't? The graphics are exceptionally good, and the game requires much more time than any other game i've played. If you absolutely have to have realism, then maybe you shouldn't pick this up. But if you want a game that's endlessly fun, then Just Cause 2 is your paradise! I'm thrilled i bought it!