I've always kind of thought video games had something of a Dr. Jekyll vs. Mr. Hyde sort of property to them. They let you get thrills doing all kinds of dangerous and irresponsible stuff you couldn't do in real life without harming actual people and ruining lives, including your own.
There are always going to be the ones who will take things too far... but honestly they were most likely disturbed and near their breaking point even before they played a video game.
I find my perception of gaming violence could be somewhat corroborated by scientific studies of pornography and its effect on sex crime...
http://www.sciencedaily.com/releases/2010/11/101130111326.htmTLDR; having an outlet for your fantasies and to take out some of the stress from your life on to that doesn't harm anyone generally will make you a better person. As long as parents keep their kids grounded in reality, there is really not much cause for concern.
I grew up playing games. Some of them were your average kid games fare like some cutesie english and math games, or maybe Commander Keen. However, I also played Wolfenstein 3D when I was in elementary school.
At the time, my father was very frank with me about the differences between games, and reality. That there are no save games and no respawns. Death in real life is tragic, and final. It's a simple talk, but it made an important point to me at an early age.
In the end, I think most of the blame for the crime related to video games falls on poor parenting, or a mental imbalance. In which case, chances are they would have snapped, regardless of whether violent games existed or not, at some point in their lives.