This game was quite a good game. Instead of killing people, like in a lot of other games, you kill huge monsters and aliens. Now, the reason the ESRB rated it "M" was because it has a lot of blood, sometimes the alien's arm will fall off when shot too much, and there is a little bit of language. But all these things can be turned off in the menu, so no more chainsaw, bad words or blood!
Also, in most games, the Muslims are either the bad guys, or not the good guys. But in the Gears of War series, your character likes Islam and later converts. He says things like "For God", or "We fight only in the way of God." You even get to save Mosques from being destroyed. But it's not racist. When a character in the game asks you to come back to Christianity, your character says "To you your religion, and to me mine."
Overall, this was a great 3rd person game, with not much violence with the settings, and Islam friendly.