IMHO like anything else, "gaming" as they call it should be enjoyed in moderation, balanced with other activities,family time,schoolwork etc.
Regarding concerns about aggression, I think quite early on kids tend learn to distinguish between fantasy and reality, and their brains don’t treat these phenomena the same.
That being said I can see how some kids could turn out a little more violent after being exposed to violent video games, especially if there's no balance in the form of other activities.
Perhaps the parents of the children that are allowed to play said games, all day everyday the ones that don't give their kids a good balance of activities need a good slap
