Honorable mentions: StarDrive, Polaris, Star Wars: Rebellion.
StarDrive 1 & 2 are awesome games made by a single guy who, believe it or not, gave up a job as an attorney to pursue his passion – making PC games!
Polaris Sector made by SoftWarWare and published by Slitherine, which are known for the somewhat more “heavyweight” strategies.
Star Wars Rebellion is one of my favorite games of all times, but one that hasn’t aged well. The graphic glitches and extremely small resolution make this once legendary game pale in comparison to its former glory.