It's a load of ****. Okay, people (/kids) have done violent things after playing some games or watching violence on tv, but it's not related. It's at people's own responsibility not to commit crimes. If anyone plays the games and copies them, they're either kids not mature enough, stupid, or sociopaths.
HOWEVER, if you're exposed to violence for a long time, for example on tv, it could lead to some sort of brainwashing. This is in my opinion apparent in the States for example. The bullshit media tell people nothing but news of terror alerts, breakins, murders, rapes, etc, so everyone gets pumped up full of fear into buying various ****, that people are made to believe will help them, from for example the "very evil and violent" male african-american age 20-30. How many times haven't you heard on the telly "suspect is a male african american"?
Now, back to the video games...unless it's long term brainwash, there's nothing wrong with the video games, once the kid reaches a certain age. And then again, long term use that boarderlines brainwash isn't the recommended usage, so people making video games are guilty of nothing.