The only game I've beaten twice is Max Payne 2. I did this because I beat part 2 before I played the original. When I eventually got around to finishing part 1, I completed MP 2 again just to see how the stories linked. The next game I'm thinking about completing again is Shenmue 1 and 2. The reason is that I don't remember anything about the games and with part 3 coming out there's no better reason not to re play these games. I really enjoyed them back then.
What about you guys? Sometimes I've seen people say they've completed a game's campaign twice, and I saw once someone said up to 50 times. WOW. This is why I must ask, apart from liking the game a lot, what are the reasons that make you re-play games that you've already beaten?