Surprisingly enough, my 4-year old really isn't into video games like his old man is. I've tried sitting him down with my NES a bunch if times. He loses interest after 5-10 minutes.
He'd rather go play with his toy trains or cars, or throw a ball around, which is great. Maybe when he's a bit older he'll have some interest. I'm certainly not going to push it on him, but if he does gain interest, I'll be all to happy to guide him in the right direction in moderate amounts. In the meantime, we like to play street hockey, kid's got a mean one-timer.