I'd also like to see more rpg's in less popular settings. Especially sci-fi. Obsidian's Aliens rpg looked and sounded fantastic.
There are good reasons we get so many fantasy rpg's however, and it's not because people just love orcs and dwarves so damn much. First of all, it's simply such a popular and classic setting that people take for granted. You get so much for free; no one will question why there are orcs in your game and no one will question what an orc is. Fantasy races, their typical traits and cultures are so deeply imprinted on us that they're almost historical subjects. Yet there's enough room for personal interpretation and storytelling. Second (and most important), fantasy almost always equals magic. And magic equals a lot more freedom for plot devices, enemies, item powers, and player/enemy skills and abilities (and as an extension, character builds).
In a sci-fi setting, even though it's fictional, people still tend to expect an explanation for how things work. It can totally be a bullshit explanation verging on "magic", but still requires more writing and thought put into it. The exception is of course already existing sci-fi settings, but the popular ones aren't exactly easy to license. And there's no generic equivalent of the fantasy setting, although it's starting to take shape with the continued popularity of Star Wars and Mass Effect. Although I would argue that both are more or less fantasy in space, especially Star Wars.
And for that matter, we're pretty short on post-apocalyptic RPGs also. Where is the zombie RPG?
Well, there's Dead State.
And I'd say post-apoc is starting to get a bit generic as well. I love me some post-apoc, but from what I can tell new games these days are either fantasy or post-apoc/dystopian.