Probably the most important aspect of most fantasy stories, magic makes the fantasy world go round. Science fiction, unfortunately, lacks magic. There are no magic baking spells in SF, no glittering fireworks spells or spells to send the evil bad guy to the fiery depths of some imaginary hell. You can't shoot magic fireballs from your hand in an SF world either, and I think that's a travesty.
- Dragons and Other Creatures You Can Ride
Let's face it. If you had the opportunity to ride on the back of a real dragon, would you? Unless you're afraid of flying or heights (or oddly afraid of fantastical critters), or simply crazy, you'd jump on this opportunity in a heartbeat. Throw in some pegasi (plural for pegasus), gryphons, unicorns, etc. and you end up with a laundry list of fantasy-based critters you can ride. Sounds good to me.
- The Bad Guys Always Lose (a.k.a. Happy Endings)
And I mean always. You can probably cite a few good examples to the contrary, but fantasy stories almost exclusively end with the bad guy losing. This doesn't happen all the time in SF; sometimes you nail one bad guy, but the evil corporation still exists, or another bad guy springs up from the same mold, etc. At least in fantasy you know that there's a happy ending. Lots of cheering and good ale. All you get in an SF celebration is the dark realization that none of it really matters, because in a week some other goon will rise up and continue with the "company mission."
- Unique Languages
True, there are a few SF stories with unique, invented languages, but fantasy rules on this front. And I do mean rules. Tolkien wasn't even the first one to do it, by the way, but he was the one person who made invented languages a cliche of the genre. But that's okay. I forgive him for that. I like Quenyan and Sindarin, or the dozens of other interesting languages that have sprung up over the last 50 or so years. They're interesting and I have the utmost respect for fantasy authors who can do it well, because I can't.
I don't mean this in the traditional sense, although fantasy draws heavily from human mythology (obviously). By this, I mean that the fantasy genre has created its own mythology, largely due to Tolkien, of course. Science fiction, with rare exception, doesn't have this benefit. The hordes of fans obsessively devoted to a particular world tend to be fantasy enthusiasts, not science fiction enthusiasts (with exception primarily to the Heinlein crowd and the folks that thing Dune is real). They have a lot to be devoted to: fantasy authors have developed entire histories for their fictitious civilizations, which have captivated audiences worldwide. It's a beautiful thing.