Interesting question, Rivka.
I had a hard time choosing, but in the end I voted for "fantasy" because the main character is an alien bing with fantastic superpowers.
That's not what attracted me to the show, though; it was the "realness" of the characters, especially Clark. Do you have a category called "real characters becoming involved in a romantic relationship with each other with some scifi and fantasty thrown in?"
Shadowfax