What are some of your favorite sci-fi games?

For me, I would have to say Sins of a Solar Empire & Galactic Civilizations 2.  The first is better at simulating fleet actions, while the latter is more of a "galactic emperor" sort of game. 

Anybody play these games or other sci-fi games?

I own both of those games too. I love the Dawn of War series as well, System Shock 2 is awesome, and you can't forget some of the Star Wars games like Jedi Knight 2 or Jedi Academy and KOTOR. I did buy Sword of the Stars a few months ago, and it's not to bad, another 4x style game.

I just picked up X3: Terran Conflict.  Seems like a good game, but it is proving to be a resource hog. 

I recieved a free copy of X3 on Steam, and have yet to get it to run. So when you have played some, let me know what you think.

Since I got sick, I haven't had a chance to get back to the game.  However, I was getting a bit annoyed with it because it seems to make the life of a newb needlessly harsh.  I like EVE's newb missions much better.  In fact, so far, I would have to say that the only advantage to playing X3 is the lack of monthly fees.