My sons are also addicted to computer games such as Sudden attack, Maple story, and etc. And, I can not stop it. We once tried to remove PCs from our house, but schools give homeworks that require PCs and internet.
Recently my eldest son was suddenly addicted to manga (cartoons), sometimes going to bed at 3 AM. But, I even encouraged it, as I think that at least manga is better than computer games.
Barbie~~