Let the Kid get any game he wants. Just check in on him 1/2 hour past bedtime and make sure he isn't still up playing... and he'll be fine. Set limits up front on how much he can play. A good side benefit to playing PC games is learning how to performance tune a PC...Trust me, he'll get good at that too.

I allow my kids to play a select few PC games because along the way it helps build computing skills, Unlike Consoles such as X-BOX, Playstation etc.. They are a waste of time IMO.