Since there is some debate going on here, I will preface this by saying that although I am personally unable to derive any enjoyment/fulfillment from something, it does not mean that I look down upon it or refuse to accept that other people can like it, and completely understand that it is obviously of great value of the people who enjoy it. It is simply my own ignorance and thought processes that keep me from enjoying it, not the other way around
OT: I don't understand "mature" games. I mean games that have very serious/gritty/adult stories. None of it ever seems to be able to captivate me. It all just feels incredibly disengaging and boring to me. Like, for say, Mass Effect. For reasons I won't go into great detail about, I came into possession of a copy of Mass Effect 2 for Christmas from a parent's friend. Since they were nice enough to get it for me, I felt obligated to make a legitimate attempt at playing it. Unfortunately, I was absolutely bored to tears by it. It was no exaggeration to say that a few minutes into each session of game play, I found myself dying to turn the game off, because I found that it was dreadfully boring, and the characters seemed so bland, I couldn't bring myself to care about them at all.
Call me strange, but I have a preference toward melodramatic characters and fantasy versus harsh realism, which is why pretty much all I play in terms of games are JRPGs, some Nintendo titles, Sonic, and the occasional miscellaneous game like Journey or Scribblenauts.