One of the best games I've ever played. I really need to finish playing it.
Descent: FreeSpace - The Great War was released in 1998 on PCs and developed by Volition, who would also create great games such as FreeSpace 2, the Red Faction series, and probably most famously, the Saints Row series. The game was published by Interplay, who also created the Fallout series and published Baldur's Gate. In the game, you pilot a variety of starfighters and perform missions.
Story-wise, FreeSpace takes place during a war between the Galactic Terran Alliance and an alien race called the Parliamentary Vasudan Empire. The first few missions in the game are focused on that war, but things quickly change when both species are attacked by an insanely powerful and advanced species dubbed the Shivan. Probably the most mind-blowing aspect of the Shivans is the Lucifer, the gigantic destroyer they deploy against humans and Vasudans both. Now, when I say gigantic, I don't mean "oh, it's pretty damn big", I mean "HOLY MOTHER OF GOD WHAT THE F*CK IS THAT THING!?" Basically, it's the biggest ship in the game. Needless to say, the GTA and Vasudans put an end to their war and buddy up to stand against the Shivans.
There are several neat things about the game. For one, you can earn promotions and medals if you do very well on the missions. You can issue commands to other fighters, such as ordering them to only target specific parts of an enemy fighter or capital ship. You yourself can similarly target subsystems and honestly, it's more fun than it should be to take out a capital ship's engines, weapons, sensors, and comms without destroying the ship itself. Another thing I like is the way the tutorials are set up as training missions. At the start of the game, you go through basic training to learn how to pilot the ship and fire the weapons. You're given the option to take further, more advanced training courses as the game progresses, each one showing you some new tricks.
You can still buy the game, even after 15 years, if you want to try your hand at it. GOG.com has it available for download for only $5.99. Not a bad deal.