One of the sci-fi flavours I love is cyberpunk. You know, Gibson, Blade Runner, Ghost in the Shell, Deus Ex, Transmet...that kind of stuff. I'm not going to talk about that here.
I've been trying to categorize the other sci-fi stuff I like aesthetically and would like to use in games. I've come up with two categories I'm going to call Pulp and Retrofuture. (Those are my terms for the purposes of this post, I'm not describing them universally.)
Pulp is little science and a lot of fiction. The vastness of the universe is just an excuse to stuff it with weird shit. If you have a strange awesome idea, there's a planet that you can put it on. Pulp takes place in that golden future age when men will be men, aliens will be green and have plastic foreheads and women will be women (sometimes green). Pretty much all science and gizmos in Pulp are just mcguffins, plot devices, magic by any other name or simply cool colour. Stick a few lightbulbs on it and call it handwavium. A lot of the machinery looks completely implausible. It's always just one step away from planetary romance (barely). In Pulp larger-than-life heroes in spacesuits fight with swords and rayguns, have awesome names, and punch space-apes in the face. It's something Lego Quest on /tg/ managed to distill very well. Like most pulp it's casually racist and sexist since exploring another planet is barely any different than going to an exotic country and shooting some natives because they speak a different language. But we're better than that.
Retrofuture is considerably more science-y. Still very fictional, but it at least looks a lot more plausible, robust, technical. It's space exploration as it would have been if the space age had lived up to its promises. In many ways it's a "blue collar space" as portrayed by the rather excellent movie Moon. It has lots of guys in spacesuits, out there alone. Rocketmen. Working. Mining or manning stations or clearing debris or towing asteroids. It deals with issues, psychology.
I think Cyberpunk, Pulp and Retrofuture are three foundation stones of the kind of sci-fi I'd like to play (but probably not the only foundation stones). Stuff can be mixed and matched. Add horror to Retrofuture and you get Alien or Dead Space. Remove some of the more lurid elements of pulp and make it British and you get Doctor Who. Etc.
It is likely that this division has strong parallels in my preferences for fantasy lately. I've been leaning towards:
*city-based fantasy that's dirty and revolutionary and magicpunkish (cyberpunk analogue)
*weird, dying earth-ish, funny, strange, sexy, action-y, wondrous fantasy (pulp analogue)
*not-really-fantasy but more like accurate historical stuff with an artistic carte blanche (retrofuture analogue)