If there were no violence in the world but people hadn't changed, violent videogames (and other forms of entertainment) would be even more popular. Our violent tendencies would have to have somewhere to go, and violence has always been the most satisfying (though not the best) best way to solve a problem or a conflict. That would not go away so easily.
If, on the other hand, humans changed and the instinct for violence completely disappeared, then the purpose of those violent games would disappear, and we would be left with Brain Training, Puzzle games and such. The gaming industry would not be where it is today, that's for sure.
This is invisible text!