My 6 year old boy loves the Wii and, in particular, the game "Scooby Doo: First Frights". It has provided hours upon hours of entertainment and has good replay value (e.g. you're not bored after you've solved the game once).

There are lots of bargain games for the Wii, and lots of animation movie-themed games.

Bears, beets, Battlestar Galactica.