Correlation does not prove causation. Just because agressive boys play agressive games, does not mean one causes the other. Both may be increased by some unidentified outside factor.
This week on TV is a special on how boys "are at risk!" Apparently, grades are falling, they are getting into trouble, and are "acting out." For forty years, the Women's Movement and their fellow travelers have be feeding us the lie that we are all the same, and trying to engineer aggression out of men. Well, boys are boys, OK, America? They are going to roll around on the ground and punch each other. We are hardwired that way.
Boys are being gelded because men are being made ashamed of what they are. The Red Foreman Dad who told you that you were expected to make something of yourself, to get out there and fight, to strive and achieve has been replaced by weak-willed and apologetic men, or all too often, by moms who are taking up the slack from Dads who won't be Dads. The end result is that the natural aggression wired into men's brains is sloping out over the sides into other behavior where it's more acceptable, or at least it was until this additional kind of nonsense takes even that away.
These whiny lab rats and their Feminazi collaborators can have my gamepad when they pry it from my cold, dead hands.