I always wanted to write a bit about the origins, inspirations of the game, so let's begin :)
Master of Orion is probably the one that influenced the design by most. To be exact, the first part of MoO. While the second part was also really good, it sometimes required too much micro-management to my taste. The mechanism that you have to improve your propulsion technology before venturing further was clearly inspired by this game.
Space Empires is another game that was really fun. My only problem was that it really required a lot of time if you wanted to be effective in it, since it was a very deep game, also micro-managing your colonies became tiresome after a while.
I already mentioned Desktop Dungeons on the earlier posts; the simplicity of the design was the main point there.
Stars! is an other space strategy that remained relatively unknown, probably due to the almost non-existant graphics. The race creation is really deep here, but this game also requires some serious commitment before it truly begins to shine.