Rise of Nations. It's like Civilization but as a real-time strategy game and I really enjoy it. Microsoft actually released an updated edition in 2014 which was good of them but I basically never hear anyone actually talk about it which sucks because it's such a cool game. The single-player Conquer the World campaigns are also cool, and have some elements reminiscent of the classic Risk board game.

There's also Star Trek: Bridge Commander, which is often mentioned in discussions of "what Star Trek games were good?" but not much outside of that context. It strikes a perfect balance between having starship combat that really feels like you're commanding a ship with a lot of mass behind it and actually being fun and easy for an average person to pick up and play (which is where stuff like the X Universe games fall down). There are tons of "space fighter" games out there but I've never really seen anything that captures space capital ship combat as well as Bridge Commander.