*Freelancer *was a nice game, with a *Privateer *feel. The space combat itself was very shoot-em-uppy (3rd person view, mouse driven, dumb AI, extremely easy) but the universe, story and sandbox aspects made up for it. You could earn cash trading and even mining asteroid fields, but you could very much make a living shooting shit up, too. For that matter, the main storyline involves liberal amounts of shooting shit up.
Tachyon:The Fringe was in the same vein, though more simulationist. It also introduced an interesting mechanic : at any time you could “cut propulsion”, allowing your ship to fly in a straight line and at constant speed no matter what your ship heading actually is (i.e. you could fly one way, with the nose and guns pointing anywhere, including directly backwards). This allowed for very tight turns, unique multiplayer dogfights, and if you did this at the peak of your afterburner-boosted speed, you could zoom past anything 
I’ll also second CutterJohn’s suggestion : both I-War games were excellent, in no small part due to the robust space physics, and the fact that for once you’re not running a nimble starfighter, but a ponderous capital ship bristling with guns.
*Starlancer *was a more run-of-the-mill dogfighting game, which felt very much like an X-Wing clone, complete with the same kind of briefings, and of course hell missions involving shooting down torpedoes targeting your carrier coming from everyfuckingwhere. The story and setting were fairly blah, and there was no freedom or exploration whatsoever. You do mission 1, move on to mission 2, etc…
As for RTS’s, nothing can touch Homeworld. Fighting in a real 3D space (albeit with a defined “up” and “down”) really takes some gear-shifting in the brain department.
It is in the wonderful world of software developpment. As you might know, the first 90% of a given project’s code takes up 90% of the dev. time. The remaing 10% of the code accounts fot the *other *90% of dev. time 