I would argue that Wolfenstein 3D is more responsible for ushering in the first person shooter genre than Doom.
Wolfenstein was original in it's technology, Doom was based on that tech. Both were extremely popular in their time. The main difference is that iD sold their Doom 3d tech (which produced games like hexen and heretic) and did not with their Wolfenstein tech.
"The game plays similarly to Wolfenstein 3D, but the graphics were changed to reflect a non-violent theme. Instead of killing Nazi soldiers in a castle, the player takes the part of Noah, wandering the Ark, using a slingshot to shoot sleep-inducing food at angry attacking animals, mostly goats, in order to render them unconscious."
.. But Doom sure felt like next gen tech to the end user. What was impressive and inspiring about id was how they raised the bar on every major release. I remember how many of my friends had to pony up for 4MB of RAM and a new sound card just play DOOM, and how they reacted the first time they played just the trial demo. It was mind blowing. That's what I like about Carmack as an example of an amazing hacker, he pushes the envelope and delivers the goods, and then shares how he did it with everyone else, even competitors. That's what really made the entire gaming industry leap forward.
I dunno, when I fired up wolf3d for the first time my jaw dropped. I never saw anything like it before.
I think a lot of people got exposed to wolf3d after it had been out a while, but with Doom they got to experience the hype leading up to the release.
I played wolf3d the week it was released to shareware and it was groundbreaking in every way imaginable back then. Doom took it to a whole new level graphically, but the gameplay was no different.
I do agree that Carmack's attitude in general was awesome, he never seems to get intimidated by competition.
If you want to get nit-picky, Wolfenstein 3D's tech wasn't original either. It was based on their previous title, Catacombs 3D, which was itself based on the tech of another previous title called Hovercraft 3D.
Wolfenstein was original in it's technology, Doom was based on that tech. Both were extremely popular in their time. The main difference is that iD sold their Doom 3d tech (which produced games like hexen and heretic) and did not with their Wolfenstein tech.