The only reason you didn't find these games on the Amiga is because of copyright issues.
That, and the fact that games like 'Zool' (which were touted as 'Sonic-beaters') were incredibly banal. I even remember magazines saying that Amigas should stop trying to be consoles, making poor clones of excellent console games, and concentrate on being Amigas! I still agree with that.
Akira: Sure, but people actively spend money on hardware just to be able to play Sonic or Mario. Just like they went out and bought CD drives to be able to play Wing Commander on the PC. There wasn't really a game like that on the Amiga, in any genre. But one things for sure, there was never an Amiga platform game that ranked anywhere near Sonic or Mario for playability. The consoles got: Mario, Mario 2, Mario 3, Super Mario World, Super Mario World, Mario World 64, Sonic 1, Sonic 2 and Sonic 3. That's 9 FANTASTIC platformers I've just listed off the top of my head.