If you're into computing history, it isn't even so much the power of the CPU (but that was certainly one bit). It had to do with how different computer architectures wrote to the screen. We take it for granted today with modern computing, but back then computer designers had to make trade off decisions to improve one area while sacrificing functionality in another. It was the age of sprites and many features were put in to handle more sprites, or more on the screen at once, or how fast you could cycle between them, or their color palette depth, or resolution. Not a single bit of that helped Wolfenstein 3D (Doom's predecessor). 3D graphics FPV like Wolfenstein and Doom changed computing forever, and many systems (like Commodore) were left behind. Even early Macintosh computers struggled with 3D FPV games.

So even Amiga and early Macs were far more powerful than c65 CPUs, but still struggled in 3D FPV.

I don’t really think you can make a reasonable comparison like that between an 8-bit CPU and a 16 or 32-bit CPU.

If you're looking for an honest-to-goodness running on C64 hardware FPS experience that is as close to Wolfenstein 3D/Doom that we've seen so far, there is a really impressive demo from jimi9757 where he made a ray casting engine for c64. You can see that here.

Perhaps even more impressive is he made a version for the Commodore PET too.