ST vs Amiga discussions were never this boring in the past! ;-)
-Edit- I'll throw my $0.02 in... A game is 3D if it presents the user with a 3D environment. So side scrollers and isometric games don't count, thus dungeon master does count IMHO. I know was was basically a slideshow, but that doesn't really matter to the user, what Dungeon Master wasn't was a First Person shooter... And this is where things get confused.
Then we have Wolfenstein (arguably the first "First Person Shooter"), which doesn't add much to the "3D genre", as we had flight/racing sims in true 3D and even carrier command which although a real time strategy game at heart had plenty of 3D shooter gameplay.
What Wolfenstein did, was take the sidescroller and put it into a 3D context. The sidescroller/platformer was the most common/popular type of game so... All games which would have been side scrollers and platformers (and thus all the games machines like the Amiga/Megadrive/SNES/etc which had dedicated hardware for 2D games) suddenly needed to be better at 3D.