Video game violence

First of all, I'm an old fart. I'm 70, yes seven zero. I have a son who was born with a number of physical problems, including a lack of fine motor control and a vision problem. We were reluctant to get him any games because we thought it would only lead to frustration but, in fact, it has lead to him getting more control over his fine motor skills and he is able to look ahead to determine the course of action. He has gained from his experience with video games BUT, he seems to favour Grand Theft Auto. The violence is incredible and unnecessary and I would like to be able to get a game that would require more thought that would hold his attention. I don't want it to be a challenge that defeats his efforts but lets him progress as he gets better.