I love Science Fiction. I love RTS, 4X games, and all strategy games by extension. I'm still waiting for Kane our Messiah to return...
Anyway, I also heard good things about Paradox games (Europa Universalis, Victoria, Crusader Kings games...).
They're very good at emergent gameplay : not imposing storylines on you, but creating an environment that makes you create your own crazy and super interesting stories. There's probably nothing like the crazy stories of Crusader Kings 2 (and all the manipulation of your blodline stuff, go read the subreddit of that game lol).
Stellaris is the most accessible of their games, and it helps that the theme (Sci-Fi) is super interesting. Lots of crazy stories about meeting aliens (and purging/humiliating them), making vassals, lots of events, exploring like in Star Trek, nearly-realistic (the government, ethics system is very logical), meeting pre-FTL civs and infiltrating them like some space lizards lol, very memeable game obviously, and very moddable. Very good writing, lots of easter eggs that show the devs' love for the source material....
I wouldn't shut up praising this game's merit. Go read /r/Stellaris . Mind blown....