Let's look at this as prime Pride HW's circa 2003/2004/2005 (Fedor, CC, Big Nog, Barentt, Coleman, Randleman, all with no USADA) vs current UFC HW roster.
Prime CC would decapitate Stipe easily and the rest of the division except he would struggle against the pressure and wrestling of Cain. However, straight left, or unexpected LHK could end Cain instantly.
Fedor would eventually drop everyone with his quickness/power and either win by TKO/Sub, though I also think he struggles against Cain.
Big Nog would Frankenstein his way to the top of the ranks, but lose every decision to the top guys like Stipe, Werdum and econoReem. All have better strikes and Werdum's BJJ is superior. I could see him catching Cain in a sub late rounds though. I think Reem beats him because he can survive on the ground now and do enough damage without gassing to earn a decision.
Barnett gets wrestle fucked by Cain, KO'd/TFO'd by Stipe, and subbed by Werdum
Coleman/Randleman could out wrestle and GNP some big players, but I see them in the same role they were in Pride. Always a threat, but still too one dimensional to worry anyone.
I haven't seen Ngannou tested enough so I can't say how he does against Pride's elite HW and I don't think Black Beast has the endurance to e a threat. Mark Hunt is better than he was in Pride, but his chin isn't the same and he probably lose to his old self and prime CC/Fedor.
In summation, it boils down to match ups, as it always does, but Pride's prime HW division holds the title, or always threatens IMO and that says a lot about how good they were, despite the 13 year gap from its prime days vs today's UFC roster.
edit I forgot Sergei but I've typed enough, curious as to other's thoughts on how he'd do.