Maze/Maze War, Chuck Yeager's AFT, Elite. Not as polished or fast as Descent or Quake on a Pentium chip but you'd need to redefine 3D with rather obtuse constraints to exclude them.

Wolfenstein 3D came out in 1992

Wolfenstein was not full 3D.

Not really 3d, the map/engine didn't support a room above another room.

This was also true for doom games, and I think hexen.

Quake was fully 3d.

Duke Nukem had some 2.5 D stuff going on that was more powerful than what doom was doing, but just barely. I think the first fully 3d game that meets your definition is probably 'Descent'