I think it's cheap and useless to blame video games for all the violence in the world. Whatever happened to that wonderful thing called "personal responsibility"? For example, I enjoy the GTA series, but I haven't gone around shooting people for fun. If someone can be that affected by video games, they're probably already mentally unstable anyway.
If you're worried about kids playing those naughty violent video games, the age certificates on the cover should tell you what to expect (granted, I played them back when I was underage, but I reiterate, I'm not killing anyone). As an adult I feel I'm capable of making my own decisions about what I can and can't play.