A big and important question in our society is whether playing video games, which people of all ages do more and more, causes more violence/aggression. Popular videogames such as Grand Theft Auto (GTA) often involves a lot of violence/murder and it would not be an unreasonable hypothesis that this could affect the person playing the game through observational learning.
I will not argue that there is definitely no effect of video game playing on violence, however, if there is such an effect it is being overshadowed by the significant decline in all types of violence that we have been through history. This trend towards a more peaceful society have in fact been particularly pronounced in the last couple of decades, that is, since video games became popular. In short, while people are playing more videogames, our society is getting increasingly peaceful i.e. there is a negative correlation between the amount of time people playing video games and violence. This pattern is more consistent with the idea that video games makes people more peaceful although I do not think data would support that idea either.
I don't think anyone will question that people are playing more videogames today but if you do take a look at these charts. If you don't believe that violence has decreased in modern times (maybe you even think that it is increasing), then you should read this excellent book by Harvard Professor Steven Pinker where he gives you all the data
Pinker, S. (2011). The Better Angels of Our Nature. Why Violence Has Declined (p. 832). Viking Adult..