The first Unreal Engine was first used for Unreal, then they decided
to release the multiplayer as a stand alone, and Unreal Tournament was
born.
For Unreal Engine 2, they released both the single player Unreal 2,

I wonder if Epic Games ever thought about releasing a special edition Unreal
Tournament (UT) that has basically all the UT99 maps, weapons, mods, etc but
updated to today's game engine and graphics.  Additionally, having the same
gameplay could make this an ideal release.   I ...