Just got finished playing Just Cause 2, a fairly new title developed by Eidos & Avalanche. I was fairly skeptical of it due to the 81 metascore on metacritic, but decided to rent it with Gamefly. At first, I was pretty turned off due to the highly repetitive missions (HIGHLY), but after exploring the vast world, I realized it offered so much more.
Playing this game merely to progress through the story will be extremely disappointing. If you end up with a copy of Just Cause 2, explore the world. Cause chaos. Do faction missions.
The world created by the developers is so expansive that I barely recall seeing the same place twice. There are all types of vehicles (cars, boats, planes, helicopters, motorcycles, etc), accompanied by a grappling hook which can be used to take you anywhere. It also allows you to launch yourself into the air and use your parachute to enjoy the free-falling experience. Imagine a plane taking off, hooking onto the plane with your grappling hook, pulling the pilot out in mid-air, hooking onto another plane nearby, hijacking it, and then parachuting out before crashing. Yeah, you can do that.
I wouldn't recommend buying this game. It's fun for a while, but can easily become rather boring. I put around 22 hours total into it and then sent it back to Gamefly (with only 22% of the game complete). I completed the missions, but completion is also measured by how many cities you explore and materials you gather.