I've played a few different space combat simulators (the obvious Star Wars ones, though less of those than one might expect, and especially Star Crusader, which I played through two or three times before the only computer that I could play it on died forever). I've also played demos for a few more. The demo I remember best was the demo for Tachyon: The Fringe, a game that sounds like it ought to be part of a series, but isn't.
The main thing I remember was that it had flexible gameplay, a super-slick control scheme, and ship customization that actually was pretty fun.
It being a demo, I didn't get to see the best part, this scene from some part of the game or another:
"I WILL NOT TURN OVER THE PRETTY CEILING! IT IS MINE NOW! MINE, MINE, MINE!" (It has to be all in capitals, because dang is he loud!)
Apparently, that's the only voicework that guy ever did. Kinda sad, because that was pretty great.