I have no idea if it’s any good, but the rogue-lite Space Tyrant–which casts the player as an evil tyrant taking over the universe–is apparently the first 5X games (it goes to 5X?),
eXplore, eXploit, eXpand, eXterminate and eXsanguinate!
The game is currently in Early Access, but TotalBiscuit has a nice look at the game.