If you have ever seen people playing some of these games they do certainly get involved pretty deeply. You can see the look of determination on their faces. They are going to kill the enemy if it is the last thing they do - and of course almost invariably it really is the last thing that their character does. They get up with a few penalty points and start all over again. Then somehow that situation is labelled 'realistic'. Yes really!
Already you might see that there is a flaw in the hypothesis that they are harmed irredeemably by the experience. All the players must realise that they are not playing a scene that they could really believe themselves to play in real life. They can't have failed to notice that in real life it would hurt to be shot or that if you were dead the game would be over.
On top of that there is no convincing evidence either way about harm. One of the good features of the games might be that their reaction times improve the more they play.
However, when I was young(er) we used to play armies, or cowboys and indians, using sticks as guns. We used to play with catapults, fireworks and air rifles. We used to dismantle electrical equipment risking death in real life. But now it seems that a Play Station is a much more of a lethal weapon. Repetitive strain injury is the biggest danger. (I'm not belittling its consequences by the way.)
But there is another comparison that is forgotten by some of the pious people who complain about video games. This is not in the realm of analogy, but a literal truth that we must face.
The threat of christianity (and indeed the threat of Islam)!
Sticking to christianity for now, as Islam is too easy a target, let's look at what children are taught about their faith. First of all we have to ask whether it is, in any way, moral to believe that our sins can be forgiven by the punishment of another person? Surely vicarious redemption by human sacrifice is utterly immoral and unforgivable in any real-life situation. Nobody can take responsibility for another person's actions in the way that is suggested by the church(es). Only by using the morals of the bronze age can the philosophy of scape-goating be proposed to have any meaning.
And yet we teach young children that there was something good about the way that Jesus died on a cross - for us - without seeking our approval to become involved in this vile ritual. We might not (often) dwell on the gory details of crucifiction, and in avoiding the subject we might think that children are not affected by it. But what child can approach Easter without wondering how terrible it could have been to be beaten close to death, and then forced to carry your own instrument of torture to a place where you will be nailed to it? Then they can imagine hanging there in agony for hours until they die. Somehow all this atones for the fact that a talking snake persuaded Eve to eat an apple.
The mental harm of wondering where Easter eggs fit into the picture pales into insignificance in comparison.
How can that be less harmful than a Play Station? Tell me! I know adults who have been damaged by christianity and who are still recovering. I don't know any adults who have been so damaged by an X-Box.