GalCiv2 + expansions
Sins of a solar empire
Sword of the stars collectors edition (includes expansion plus other goodies)
Space empires V
Star Wars: empire at war
Imperium galactica 2
Star Wars: supremacy
Star Wars: galactic battlegrounds (the game which let me know I'd had enough of RTS games)
Star wars: force comander
Homeworld
Freelancer
If freelancer counts then X: beyond the frontier and X3: gold probably do too.

Some of those have yet to be played (SE V, SotS, X3, empire at war) Others have been played to death and beyond

I played the demo of BotF heavily yet never owned it. I couldn't afford it when it first came out, and couldn't find it later.

Sword of the stars was panned when it first came out so I ignored it totally. Then a bit ago I saw the announcement of the expansion on the quartertothree forums. The thread filled up with people declaring their love for the fully patched game plus first expansion. Can't wait until I get chance to settle down, read the lengthy documentation, and install the thing.



Sins wasn't all that for me either. It felt too much like age of empires and those other RTS games I got sick of many years ago. Start small, spam research and resource gathering, build flash army, skirmish while you build uber army, slowly stomp all over your enemy's base and win. Not enough to do away from that line, not enough variety from game to game. I haven't tried it with that big patch they released a bit ago; that's supposed to alter a lot.



[quote=Since I'm currently playing vanilla GalCiv 2 (I'm waiting/hoping for a full bundle to be released in an actual box), I have to ask: How does the AI compare? I know it received a major upgrade in Dark Avatar, and again with Twilight of the Arnor.[/quote]
It's been ages since I played vanilla Galciv2, and I'm not terribly aware of what AI tweaks have been done on it since Dread Lords release, so take this view with a measure of salt. It's a good improvement. The AI is less vulnerable to typical cheese, and has fewer senile moments. New strategies have been added to its book. I think it processes its turns faster. Obviously there's a lot which has been added specifically for the new features such as the race specific tech trees.