other than v-tech, what are good educational ps2 games that a 4 year old would like?

[3 more weeks till #3]

Are there any leapfrog games for ps2 or is that a whole different game thing? I don't know much about video games. My son loves them though and I would like for him to have more of a choice of what to play. I'm looking for games that are on the cheaper end of the scale too. Thanks!
he is hooked on socom right now and i'm trying to get him away from any games like that one.