You are saying PRIME Fedor would been champion in the UFC HW division. Ok
PRIME Fedor was at his peak between 2004 and 2007 in PRIDE.
Fedor defeated the likes of prime big Nog , Cro Cop, and a jacked to the tits Mark Coleman. ALL who were respectfully one dimensional fighters although great at that one dimension. The reason Fedor was so dominant at that time was because he was good at everything. A complete ENOUGH fighter to hang with those wrestlers, BJJ black belts and strikers.
Prime Fedor also fought some freak fights against 390 pound ZULU....7'2 HONG MAN CHOI....and guys who were great but smaller like Matt Lindland.
Fedor started to show a little decline in 2008 when he fought Andrei Arlovski a legit test and a former UFC HW champion and Fedor was actually losing the fight until Arlovski backed Fedor into the corner leaped into the air with a flying knee (I believe) and got caught with a solid punch knocking Arlovski out cold.
So, if "Prime" Fedor was in the UFC in 2004 he would been fighting either the young submission killer that was Frank Mir or Prime Andrei Arlovski who was much faster and dynamic than when he fought Fedor years later when he was no longer in the UFC.
I liked Fedor, would he have become UFC HW champion in his prime? I think saying he wouldnt would be absolutely ridiculous and I almost would put money on it that he would beat UFC Arlovski, Frank Mir, or UFC Tim Sylvia (he destroyed post UFC Sylvia) but would I bet on Fedor having had that many title defenses? No.
I think Prime Fedor would have MAYBE beaten Randy Couture in 2007 but I DO NOT think Fedor would have beaten Big Nog at that time in his career or even Shane Carwin. At that time 2008-2009 Fedor was nearly beat by Brett Rogers he def lost that first round. His power never changed but Fedor started to decline. Brock at that time would have likely been able to wrestle him like Big Foot Silva and do the same thing to him.
I dont think Fedor would have beaten Cain or JDS.
Fedor would not have defended the belt 10 times. Would he have become champion? I wouldnt bet against that it was at the time most certainly possible.