Criminally underplayed. Each of these deserves ten times its player count — get in before everyone else does.
5 games · every one clears the PlayBound Bar

Start with one ship. End with a galaxy-sized set of problems.
SpaceRPGSimulationSpace Trading

Physics-driven RTS where terrain is a weapon.
RTSStrategyPhysicsTerraforming

A 2D galaxy of freedom, factions, and consequences.
SpaceRPGOpen WorldFactions

Design your own tanks. Then design better ones.
RTSStrategyUnit DesignCampaign

Build the base, join the swarm, and fight the war from both sides.
FPSStrategyAsymmetricTeam-Based
PlayBound's top pick is Endless Sky — Start with one ship. End with a galaxy-sized set of problems. It runs on Windows, macOS, Linux.
Yes. Every game in this collection has been tested, played, and assessed against PlayBound's published criteria — worth playing, worth what it costs, and respectful of the player's time.