The world seems to have rewritten history, and forgotten Ultima Underworld, which shipped prior to Doom..

Couple "3D" games shipped before Doom. Battlezone comes to mind.

The difference is that id owned the natural progression (from Wolf3D through Doom to Quake) and laid foundation to what we call today a FPS genre.

I think that's because it had such high system requirements that very few people could run it, unlike Wolfenstein 3D and Doom.