Super Monkey Ball and the first sequel were among my favorite games for the Gamecube.  My family and I spent hours and hours getting those adorable little monkeys where they needed to be.  The minigames, too, were a whole heap of fun.  The Wii's Super Monkey Ball Banana Blitz just didn't have the same charm, for some reason.  The newest game in the series, Super Monkey Ball Step & Roll, adds in co-op, which is certainly a step in the right direction.