Not so much Amiga wasn't as fast as PC at the time, but rather something with the bitplane based graphics system not being suited for the psuedo 3D kind of games.
Not so much Amiga wasn't as fast as PC at the time, but rather something with the bitplane based graphics system not being suited for the psuedo 3D kind of games.
Amiga coders compensated for this with very fast, insanely optimized assembler code. They were so good that a multiple times computationally slower Motorola processor would run a Doom clone at the speed comparable to a contemporary PC bucket.
Never.
You just could not get a VGA-on-i486 level rendering performance out of 256-color AGA fullscreen, even with Motorola 68040 on the Amiga 4000.
All the fast 3D demos and games I saw were partial-screen, with 2x2 pixels, or both. Good-looking ones were slow. An example with at least some commercial success was Alien Breed 3D. Check the video here: https://www.youtube.com/watch?v=ksQG8vnvlpg
Because it was so hard to do per-pixel rendering on Amiga all these 3D graphics demos and games on Amiga basically concentrated on delivering the graphics only, with shallow content and amateur-grade playability. Doom had a lot else going on despite the smooth graphics, and that actually made Doom a good game.