My kids, even the 2 year old, have played Wii sports and I'm amazed that they can pick it up and really play the games so easily.
The issue I have with both the PS3 and Xbox 360, is that even if the games were there for younger players, the controller doesn't fit their small hands.
On a side note, I'm also considering setting up a computer stocked with all the classic arcade ROMS and an emulator, and running it through as one of the inputs on my home theater. I know the news games are fun and all, but you still can't beat a good game of PacMan or Street Fighter with an old school arcade joystick. Except, now I'll be sitting on my couch with it.