IMO, it's potentially possible for Stipe to surpass Fedor, but unlikely.
Fedor did fight a couple "cans", but he also beat:
-Noguiera twice (while Big Nog was in his prime no less, and on the ground where Nog was most dangerous on top of that)
-Cro Cop in his prime (and out struck him no less)
-Coleman (and even though the former HW champ was not quite what he had been when he beat Severn for the UFC's HW Belt, he was definitely still relevant and a dangerous opponent at that point in his career)
-Randleman (again, still a very dangerous opponent at that point on his career)
-Sapp (say what you want about him, but at that time Sapp was coming off a win over Big Nog and was definitely far from being a "can", at least when it came to MMA)
-Arlovski (again, even though Andrei had lost the UFC Belt to Sylvia, he was just coming off a win vs Werdum and was still a very dangerous opponent at that point in his career)
-Sylvia (say what you will about Timmah, but the dude defended the UFC's HW Belt as many times as anyone else has so far; perhaps this still doesn't qualify him for top 10 HW GOAT, but he was still no joke at that point)
And the most important stat was that Fedor went unbeaten during his prime. Miocic has lost to Dos Santos and Struve in the recent past. Sure, no shame in losing to the former champ in Junio, but Struve?! To me that means he's gonna have to defend the belt at least another 3-4 times till I'm ready to start considering him over Fedor as GOAT HW.
Just my opinion though.