On the surface a lot of the GC games seem totally lame. But there a couple "kiddie" games for it that are actually quite a bit of fun. Pikmin and Monkeyball are excellent games as well that have gotten much attention because of the presumed gaming level that the packaging shows. But I got to tell you these two games are louds of fun and hard as $#!+. It was proven to me that you can't judge a game by its cover
I got a PS2 as well and just finished MAXIMO: Ghosts to Glory. Quite a lot of fun as well if you dig the Ghosts and Goblins video game from the ol' days of NES.