Get him started on the PS3, and inundate him with GTA, Bully and other games like those.
Just kidding!
You can't go wrong with the Wii. There are lots of games that the whole family can play. And they are probably pretty easy for the younger crowd to pick up as far as the controls go.
But you can also pick up one of the other new systems for yourself. If you ever wanted to play more adult games, or more button orienated.