He has Game Cube and about 6 or 7 games. We play Sonic the Hedgehog games together. He loves those. He also is becoming a little savvy with the PC, which is another reason for his upgrade along with more demanding kids games.
And I'm not really overworried. Just erring on the side of caution on an impressionable child. When a child is this young, you can't be certain he/she can differentiate between shooting somebody with guns in a game without remorse or penalty, and real life.
Some do, some don't. And until I know the answer for certain, I'll assume he doesn't.