As a mature, 20's something gamer, I like to think that I am able to listen to any music I want, watch any movie or TV show I want, and most importantly, play any game I want. Doing all this, I suppose, without being in the least bit offended.
Chances are, that if you're big into gaming, there's a chance that you're also big into the sci-fi genre. While a lot of crown jewels that fit under this classification are aimed at either a younger audience or an all around audience, for example, Star Wars, many of them take pride in catering to a more mature demographic. Examples of a more adult world would be the one painted for us in The Chronicles of Riddick.