We're like that with other things too. Television shows, for instance. There are shows that we both started out liking, and one of us lost interest, while the other stayed interested in watching it. I introduced her to Torchwood, which I am over and she's still crazy about. For some reason I've kept watching Heroes and Chuck, and she bailed on both of them.
We do that with food too, with a lot of stuff. That's OK though, because we don't have that sort of weird "up each other's asses" relationships. We're both cool with me going out wandering the streets, or with her watching 2-3 episodes of a show I don't like while I go do something else. I'll go eat places that she doesn't like, and I'll go to two different fast food places for lunch. We don't both have to be doing the exact same thing at the same time, constantly. Really, that's not even a healthy thing to do. I'd rather she not feel pressured to be into everything I'm into, and I'm sure she's glad that I'm not dragging her everywhere. And I'm more than happy with the fact that she doesn't expect me to sit through her chick flicks.