Super Monkey ball: Banana Blitz is a great little game. The main game though is shoddy, verging on pathetic, and takes about ten minutes to complete. (Thats the bit with the little monkey dude in the ball as you try and roll him around the course collecting the bananas) but the mini games are exceptional.
You can play with between one and four players, the downside for me being that some of the games require a nunchuck, and I only have one, as, I would think do alot of people as they are so expensive to get the full controller. But there are still plenty of games that can be played with just the Wii remote. There are so many games to play, some obviously far better than others, but the guys who made this game really pushed the boat out, and must have had some pretty intense brain-storming sessions.
Highly reccomended.