[HoneyBadger]

Star Control 2, actually.

You might know it better as The Ur-Quan Masters. That's the free (and best) version. The source code is also free, I believe.

It's basically the most complete gaming experience you can get in a space game. It's got role-playing, good story, really evil villains, a few dozen fairly fleshed out unique/interesting/bizarre alien races, actiony space combat, a sense of ownership, a great sense of humor, some strategy (a bit too light for my tastes, but it's there), a comfortable level of graphics, and a heck of a lot of depth. It's even free. I just wish it A: didn't have a time limit, B: wasn't a click-fest when it comes to combat, and C: had more strategy and open-ended sandboxness (it has them, I just want more, because I'm greedy).

If Master of Orion is a 4X game, then Star Control is, like, 9X. It really gives you a sense of being inside of a good classic space opera.