Most open-world sandbox games have some replay value, since you can approach each situation differently each time, and Just Cause 2 is no exception.

Once you finish the main story, the game allows you to keep playing and try all of the missions you haven't finished yet. Getting 100% completion will take an insane amount of time, but there's not much incentive to replay the game once you've done that.

I rented it from GameFly and decided to keep it because it's one of the best games to go to for 2 hours of mindless fun and explosions, when I'm in the mood.