Doom was the first "supposed-to-be real" 3D game. Wolfenstein 3D wasn't really 3D in the meaning of the word, where Doom compared to Wolfenstein 3D was already further advanced. And the mood in Doom, surviving against tons of enemies and being a hero, it certainly inspired quite many players, as the statistical numbers tell anyway.
Dark Forces and Duke Nukem 3D came later, and without Doom these games wouldn't be here today. Doom started it all, and Doom 2 was a little improved Doom 1 with 1 new weapon and much better levels and more interesting enemies.
Don't forget the roots.