There are also the X3 games from Egosoft (e.g. Terran Conflict/Albion Prelude), which are great fun for building a space trading empire, exploring, waging war or being a pirate. Warning: they can suck up a lot of time. They aren't the easiest to learn games and there's a lot of modding potential. They started with a lot of bugs, but are much more playable now.
X4 Foundations is the new release, but I haven't tried it personally yet.