My 4yr old loves playing games on the computer, but I need and want my computer throughout the day. I searched for xbox 360 games for pre-school and found these links.
Common sense you can actually search by age. But alas, none for xbox. Only for wii and nentendo DS.
This is an article that points out some younger children's games.
Wii has sooo many pre-school games. Which is great, if we had a wii. Seriously xbox needs to get with it.