If you haven't played this, what are you waiting for!?
I haven't had as much fun playing a game as I did playing these. It was challenging at times but very approachable. The open-ended gameplay let me pop it in for an hour and screw around the game world if I didn't have much time or go plowing through the storyline if I had a few hours on the weekend.
I could spend a few prargraphs gushing about these games but it just wouldn't do them justice. Please, for the love of all that is gaming, just go out and get it. You'll have hours of entertainment to thank yourself with.