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.
http://www.commonsensemedia.org/reviews?media_type=29233&recommended_age=4
This is an article that points out some younger children's games.
http://deborahpercy.suite101.com/xbox-360-video-games-for-toddlers--preschoolers-age-3-4--5-a283324
Wii has sooo many pre-school games. Which is great, if we had a wii. Seriously xbox needs to get with it.