I Had 060 in my A1200 yes it could run Doom but only at 320 x 200 where as lets say a P3 could run it at least 640 x 480 maybe even 800 x 600. Even the new vampire is only just managing 640 x 480 on some games. It was the lack of GFX advancement that killed amiga along with %&$#?@!%&$#?@!%&$#?@!%&$#?@!y management.
Doom didn't even support higher than 320*200 for a few years. It was only with some later ports that resolution (other than screen size) was changeable.
Also, a Pentium, let alone pentium2 or 3, didn't even exist at the time of its release, so such a comparison is, quite frankly, dumb.
Not to mention the fact a higher resolution does nothing for the game.
Even aga + a fast 68k system can deal with doom as intended, reaching the games original frame rate cap of 35fps.