Super Mario Bros 1 2 3
Super Mario World

see wheere Im going?

Who you calling fat?  Some of us actually like to keep in shape.

Cosmic Family on Wii -- you should be able to pick it up for about $20 and it does not require any reading.

Downside is that your son will probably outgrow it in a year or two. My soon to be 6 year old son no longer plays his. He want to play SSBB and LoZ:OoT instead.

Also, Boom Blox is something you can do together -- though I am not sure you want a three-year-old "throwing" the controller.

Finally, Kirby games usually appeal to younger gamers but might still be a bit much for a three-year-old.

Mike from Morgantown

This kid.. and you know he's been playing games since he was 3...

A good GTA game will put him to sleep.

Many games designed for little children are crap. Not because they are cute or simple, but because they are ugly, with terrible controls. As if the designers had thought "the kids can't play ayway"... I bought some for my sister's children (aged 3 and 4,5) but now I play with them some great plaformers like psychonauts, or the simpsons hit and run as they love Homer. I even play Sands of time with the older and I can't believe how good he alreday is with that game ! Obviously, they never play alone and I am careful not to let them see anything violent if I'm not with them. On the PS3, they just love Ratchet and Clank. We never play more than half an hour at a time anyway...

now I'm hesitating between Siren, GTA and Postal for the next step ^_^

DO NOT BUY THIS PIECE OF CRAP! My kids went through 3 of them in less than a year. The stupid AC plug connection kept breaking and many times it wouldn't read the games. I threw it away and have been focusing on Wii games.

They party games are really good. My kids 4/5 like Sonic and secret rings, Mario PArty 8, Wii sports Bowling and boxing, Wii play in general, etc.

oh also, they really like Mario Kart Wii.

I've seen some good pre-school games lately. Go Diego Go! is a good one for the Wii:
http://wii.ign.com/articles/856/856904p1.html
Smart Girl/Boy Playhouse for the DS
http://www.amazon.com/gp/redirect.html%3FASIN=B000RZ8Z8W%26tag=askville-20%26lcode=xm2%26cID=2025%26ccmID=165953%26location=/o/ASIN/B000RZ8Z8W%253FSubscriptionId=0N1YGFKC9QHMHQ9QTDR2
http://www.amazon.com/gp/redirect.html%3FASIN=B000RZ8Z8M%26tag=askville-20%26lcode=xm2%26cID=2025%26ccmID=165953%26location=/o/ASIN/B000RZ8Z8M%253FSubscriptionId=0N1YGFKC9QHMHQ9QTDR2

Cars for the Wii is good for tkids too.

V-Smile is the greatest console of this generation! VGChartz doesn't acknowledge it because it's awesomeness dwarfs anything else. The fact that I own the PS3, Wii, 360, and V-Smile (V-S, for the hardcore) puts me on a whole 'nother level! Now excluse me while I go play Blues Clues!

Get a gamecube controller and Super Monkey.Ball. 1 and or 2. My 3 year old loves them, easy to control and help them think about each level.

The Gamecube controller is.also the best Mario Kart option for a 3 year old, my daughter places top 5 on the 50 cc races with it, she's too wiggly for the wheel, and can't master the mote/nunchuck.

She also uses it for Brawl, well who doesn't?

I second Super Mario Bros 1 2 3 and Super Mario World as well.