Sorry I missed this thread, treismac
Busy bee lately... But this is my cup o tea...
My 3 year old plays Punch Out on the NES. Glass Joe only of course. Simple enough to get him started.
Also, Trojan, on the 'VS' setting, is a great trainer. Jumpo, block, swing, all without the game trying to hurt him. I have to play then too, but it's worth it. Lot's of games fall into these categories,
but the real important thing (in my experience) is not to start thrashing the game he's playing in front of him. If he wants to play Tony Hawk 2, for example, that means daddy plays. I got too far in front of him.
And for the fun stuff, To The Earth is aces with kids. As is most games that talk.
But honestly, get a Vsmile. It's made to teach them. My son still plays Spider Man on it, and he has plenty of options. And he cruises through those games fairly well for his age.