@zeds; I know you said that ths was a question of when such games as opposed to movies was appropriate but the principle remains the same. Although not yet a parent I can imagine that I would put an age limit that the kids must reach before being allowed to view certain content. That is however largely due to the fact that Mrs Id would put her foot down and I ain't gonna argue, or so I reckon.
In my case however some of the first movies I can actually recall were Dirty Harry and The Shining. Of course, I do recall queing up to see the equally violent 12's rated Star Wars, as we now know it Episode IV, the first one,
. My point is that I was fed a healthy ration of 18's rated flicks from a very young age by my now to be eternally damned for poor parenting folks. Did me no harm what so ever. No little neighbourhood dogs tortured, no bullying in school, no late night attacks on young girls, just bloodsucking capitalistic vampirism.
The balance of input is what is important. Everything in moderation. I grew up with caring parents, with open discussion in the house where maturity was encouraged (that part was missed on me). I also watched and read films and books with softer and philosophical content. This meant that I was not overdosing on a diet of violence and was not starved of the ability to think for myself.
A cartoon I once saw:
Picture of 2 children playing behind a sofa. Legs of 2 mothers standing beside.
Mother A to B: "I just cannot believe you gave Johnny a toy gun to play with. I would not give my young Bobby a toy which encourages war and violence I try to take a more constructive and educational attitude to play."
In the picture the children are playing with Lego set, one named Bobby has built a gun and is firing at his mother, Johnny is using his gun as a hammer to aid his construction of a Lego house.