Games like X3: Terran Conflict
Games like X3: Terran Conflict include X4: Foundations, X Rebirth, Elite Dangerous, Stellaris, and Kerbal Space Program. We matched them by the tags players give X3: Terran Conflict on Steam (Space, Simulation, Sandbox, Sci-fi, and Strategy): closest matches first, and among equally close ones the better-known games.

X4: Foundations
Shared: Space · Simulation · Sandbox

X Rebirth
Shared: Space · Simulation · Sci-fi

Elite Dangerous
Shared: Space · Space Sim · Simulation

Stellaris
Shared: Space · Strategy · Sci-fi

Kerbal Space Program
Shared: Space · Simulation · Sandbox

No Man's Sky
Shared: Space · Open World · Sci-fi

EVE Online
Shared: Space · Space Sim · Simulation

Hardspace: Shipbreaker
Shared: Space · Simulation · Sci-fi

Dyson Sphere Program
Shared: Space · Simulation · Sci-fi

Rebel Galaxy
Shared: Space · Sci-fi · Open World

Space Engineers
Shared: Space · Sandbox · Simulation

Starpoint Gemini Warlords
Shared: Space · Simulation · Strategy

SPORE™ Galactic Adventures
Shared: Simulation · Space · Sandbox

Avorion
Shared: Sandbox · Space · Space Sim

Endless Sky
Shared: Space · Sci-fi · Simulation

SPORE™
Shared: Sandbox · Simulation · Space

Jurassic World Evolution
Shared: Simulation · Sandbox · Strategy

Starminer
Shared: Sandbox · Space · Space Sim

X3: Reunion
Shared: Space · Simulation · Strategy

SpaceEngine
Shared: Sci-fi · Space · Sandbox

Kerbal Space Program 2
Shared: Space · Sandbox · Simulation

Starfield
Shared: Space · Sci-fi · Open World

Universe Sandbox
Shared: Simulation · Space · Sandbox

RimWorld
Shared: Sandbox · Strategy · Simulation