I bought both Freespace and Freespace 2 not long after they came out, and recently while looking for games to play on Linux I decided to try to run FS2 under Wine. This didn't work, but then someplace in the back of my mind I dimly remembered that Volition had long ago open-sourced Freespace 2. Back then, I didn't have a Linux system worth playing games on, and I was dual-booting Windows anyway, so it didn't matter. But today, I run only Linux (aside from virtual machines - which aside from VMware Workstation, don't support 3d graphics yet) and so the Linux port had become relevant.
I'm something of a science fiction freak. It's my genre of choice whether we're talking about novels, movies, or video games. Thus, when I encountered Gate 88 I thought I was in heaven.
Gate 88 is a fairly simple top-down realtime strategy game in which the player is represented in the game - by a space ship. As you fly about you can build structures (provided you have sufficient resources) and your goal is to protect your base. You can build factories to produce more resources, research labs to develop new technologies, shipyards which (shock, amazement) produce ships, and various types of turrets to protect your base defenses. The game is designed with a very console-game sensibility in that it is ideally played with a gamepad, and playing with a keyboard will drive you absolutely insane.
Oolite is a clone of the classic space trading/flying/bounty hunting simulation, Elite. Elite is an epic-scale game with primitive graphics, although simple 3D wireframes were quite advanced in their day. Oolite is basically a modern, extensible version of the same game, which also has "primitive" graphics for the time. In this case, the graphics are fully-textured and implemented in OpenGL, and the game is pretty easy on the eyes (albeit not gorgeous.)