As I have mentioned, my mind is starting to gravitate towards Mongoose Traveller for my next outing as GM. However, I have never run a science-fiction campaign before. I find that the genre of science-fiction has a few problems for me:
1. I am a nitpicker to the extreme
2. I am far too detail-oriented for my own good, and
3. I hate making alien races. Hate it. I hate it almost as much as I hate making pantheons for D&D games. (Hence my recent embrace of just ripping off Christianity or other monotheistic religions)
Aliens in science fiction are a troubling thing to me. Earth has countless human ethnicities, cultures, languages, and other attributes that make our world such an interesting place. Aliens, as presented in sci-fi, almost always have a monoculture, mono-language, and mono-everything.. In fact, any given alien race is usually defined by one or two exaggerated human traits. Klingons are aggressive and honorable. Puppeteers are manipulative and cowardly. Vulcans are logical. Ferengi are greedy. There are usually token characters who are characterized entirely by the fact that they are the exception to the race's rule. Ah, here's the Good Member of an otherwise Evil Species, or the Brave Member of the Cowardly Race, the Individualist Member of the Hive Mind Race. Aside from personality characteristics, aliens are often relegated to a particular vocation: the warrior race, the merchant race, the scientist race, the psionic race, etc, etc.
Don't get me wrong... there are lots of alien races in sci-fi that I think are cool, even the simplistic ones, but.... I have trouble creating any that I am satisfied with. I feel like I'm just re-skinning other sci-fi aliens, who themselves may in fact be re-skins of earlier sci-fi races. (By the way, I know that technically I should be using the word species rather than race, but old habits die hard, and I've been misusing the word race in gaming since I cracked the AD&D 1st edition DMG in 5th grade. Sue me.)
I suppose there isn't anything wrong with re-skinning (a fancy word for stealing in this case) stuff I like for a campaign... it just feels lazy.
In the end, my races will probably just be amalgamations from my favorite sci-fi franchises (Star Wars, Star Trek, Battlestar Galactica, Mass Effect, etc)
Odd that I didn't have this kind of block when I came up with my Mutant Future stuff.