I could probably only tell you the basic plot of Just Cause 2 if I had to. It is not because the story was bad or anything, but rather it just seemed to be in the way of blowing everything up. That pretty much sums it up, Just Cause 2 is an open word action game with a ok story to it, but you won't really remember it because you will be too busy grappling hook parachuting off of cars.
Just Cause 2 isn't that different than the original Just Cause. You star as Rico Rodriguez, a general action hero, who is dropped off on a tropical island in order to stop the bad guys. The beauty of all this is that after the first 3-4 missions you can achieve that goal whenever and however you want to. The island becomes the proverbial "sandbox" that you are free to roam. You unlock all more missions by creating chaos. The basic premise of how this works is you find one of the bad guys buildings and blow it up. If you blow it up more impressively than you earn even more chaos. Chaos is what moves the game forward and chaos is what moves you to play more.
Visually speaking, the Island of Panau is stunning. Most games made with a decent budget these days tend to look good, but Just Cause does a fantastic job of making all its diverse environments(jungles, snow topped mountains, deserts) really pop. Overall you can really see all the texture and detail that the designers have put into the 400 square mile environment. They were also considerate enough to add over 100 different types of vehicles (cars, boats and planes) to make traveling around Panau that much easier.
There are some sand box style games out there that try to restrict you in the beginning. The strength of Just Cause 2 is that they do the exact opposite of that. They give you total freedom and let you find your own way. Want to do some side missions? Sure, go ahead. How about you just feel like running around and exploring? That is fine too. The control scheme used to control Rico works incredibly well, you can deploy his grappling hook with one click and fly in that direction, while another button will instantly deploy his parachute. This makes getting away from your pursuers (probably mad at you for blowing up there communications tower) a lot more fun and enjoyable than it probably should be. It never gets tiresome driving at high speeds off a cliff and releasing your parachute in mid air to glide into the safety of the ocean.
Overall, I completed the main story and side missions in 35hrs. That does not mean I have stopped playing the game. I currently have 70hrs logged and am still only around 50% completion of all the challenges that are offered. That is not a problem though, since I am not opposed to more grappling hook parachuting explosion filled fun times!