The only rpg I remember that was actually “to play sf” (as a genre) was Shock: , most other “sf games” actually are based on a single book or TV series or a specific kind of dystopia, or something like that. It’s not strange, seeing that when most players say that they want to play “sf” they really want to play Star Wars or Firefly or Star Trek (I don’t know if I am explaining myself: these ARE sf shows, shows that asked “what if”, but PLAYING in them is not: it’s not asking “what if”, it’s “return there, I liked that”: it’s for this reason, I think, that playing in them doesn’t “feel” like sf)