What's a Good System to Regulate my Sons's Video Game Behavior?

My 6 year old loves video games- but they bring out the worst in him when he plays alone. Unfortunately, we can’t sit and play with him every time. Example- let him loose on a computer game- like Phineas and Ferb. An hour later, it’s time to eat dinner, we call the family down and he freaks out and loses all control- yelling, stomping, crying hysterically. We talk to him about this behavior not inspiring us to let him play more later but he just doesn’t get it. After dinner, we let him loose on the playstation- doing a Spyro game (my point is that these aren’t violent games). An hour later we announce its bath time and he freaks out- hysterical, throwing things, just plain nuts. I know we can eliminate them altogether, but we want to use it as motivation for good behavior- and it causes bad behavior. Help!!