yep, i also think Doom on PC kindoff killed the Amiga.
I had a Amiga 1200+1.8 HD, damn it was fast, took around 4 sec to boot into Workbench.
Later i got Doom 1+2 running on the Amiga and it had much better graffics than on the PC
But after that it was like there didnt come any new games and thats when i bought a AMD+Voodoo2 card.