I've always thought that Tolkien was a good at story telling just not a good writer (if that makes sense) and film is a much better medium for his books. Now it doesn't help that I'm no big fan of fantasy settings in the first place and sci-fi doesn't hold much appeal to me either which considering I used to a very keen AD&D, and others, player may sound a bit strange. Saying that, lumping genres together and saying they're all the same is always somewhat simplistic. So Alien may be a classed as sci-fi but it's not really is it and the same goes for Blade Runner.
Of course you then have Red Dwarf, which is excellent, and the only sci-fi/sit-com that I can think of.