Descent will go down in history as being one the best cases for motion sickness with gamers. This series has also gone through more changes and variations than a Kardashian television show. Starting out as a 3D tunnel exploration flight sim that literally had no up or down, sort of like space but without the openness. As the series progressed, it was understandable to see the series finally hit space in the aptly named, Descent Freespace: The Great War which coincidentally is now available on Steam.
Descent Freespace is a modders dream where just about everything is up for grabs to be changed. People have taken the base game and created mods that recreate some pretty damn amazing battles, moments and scenes from other media. Ships, both yours and the those of the enemy, and even the story have been modded. This level of customization has helped keep Descent Freespace in the minds of gamers for years after release.
For an idea of the breadth of the mods available, there are ones for Babylon 5, Battlestar Galactica, Wing Commander and even Star Wars.
Some places to get mods from:
Descent Freespace: The Great War is available now on Steam.