It really depends on what their interests are. If you are really looking to introduce them to gaming, what you might want to try is getting them involved with watching you play a game you think they'll be interested in or the cutscenes and whatnot, but make sure they're engaged in it. It's much easier to introduce a child to gaming for this reason, because every part of any game or novel experience will intruige them.
It's probably not something that will happen overnight, but teach them about the controller starting with, well, the fact that it controls the personalities in the game as well as the gameplay. Let them give it a shot at times with games that are easy to get used to, games you would otherwise not consider playing because they aren't challenging enough or too childish for you, for instance. Then, work your way up to introducing them to more and more challenging games and by then, they'll possess enough skill with the controller to really enjoy games with depth like Assassin's Creed, GoW, etc. You won't get anywhere if they aren't interested, though, so find something that will interest them. I ran into this exact same problem with a few of my past girlfriends and this method worked out pretty well.