Great question. I don’t play video games as much anymore, so I forget what the rating M is, but I assume it means Mature content.
I don’t think there is anything wrong with playing a video game. But I think you should limit crazy types of games, and I will add that if the game has any nudity or extreme cursing I probably would avoid it personally.
The reason is that our minds are like a sponge, and no matter what we do, we can’t help to pick up on things we are around. Go hang out with a bunch of people that curse every other word for weeks, and you are highly likely to start using those same words. Habits are contagious, just like a common cold. People pick up habits unconsciously, even if they don’t like the habit.
So I don’t think it is necessarily a sin or wrong to play a video game that has some mature elements (again, I would completely avoid these pornography type games, or heavy cursing). I would avoidd those type of games simply for the fact that you are really going to invite bad influential things into your life, when there are tons of other ways to entertain yourself (or other really fun games), that won’t invite such negativity into your life.
But if the game just has a bit of mature type content here and there, I don’t see anything wrong with playing it occasionally for entertainment.