Well there is a LOT to talk about here actually but I'll just say a few things.
I don't think violent games are bad for kids but of course there is a limit, my biggest qualm about the whole "violent games are inappropriate for kids" is how isolated it is, I mean, the media expects to blame videogames for influencing people to be violent but there has always been violent people.
Does this mean you can just go and make your 7 year old go and play Postal or something? Well yes and no. I say no because the real problem is not video games (or movies or anything else) but parenting, there is nothing wrong with letting your 7 year old son play Grand Theft Auto or anything just as long as you know it isn't really affecting him on a real level.
What I'm trying to say is, it all depends on how a person can tell fantasy from reality and its not a matter of age... you can't classify people by their physical age, we all know the mental age of a person varies wildly, someone who is 12 might have the same mental age as someone who is 23, yet the 23 guy is allowed to drink, drive and play violent video games... its an easy way to sort people but not exactly effective.
I have a little cousin, he really enjoys GTA Vice City, he is 7 but I really see no problem in him playing the game simply because when I see him playing its like any other guy playing, he does the missions, he likes to drive, he shoots people of course and all but he knows its all fake... after playing he just goes and do whatever a regular 7 year old would do... then I see a 17 year old play it and he is more affected than my cousin... so really, what the hell?
So my whole point is, its not a matter of physical age but rather their mental age, if you want to be a good parent, try to find out how your child's mind works and let him do this and those things accordingly to let him grow by himself.
Isolating issues is never a good idea, there is this little phrase that says "Guns don't kill people, people do" and while its a little cheesy it does illustrate my point exactly, we should stop blaming everything and try to find the answers within ourselves, we all have after all, a rational part to our beings (even if the emotional part is still the dominant part of us).
Excuse me for my English, I'm not a native speaker and I'm trying to use words that are already complicated enough in my native language