I rank as if all the fighters in teh scenario are/were the same weight naturally. And then i use my Noodle to figure out who is the most talented.
My top 10 p4p are those who i think are the hardest fighters to beat due to their style and skill.
Fedor is my p4p #1 because he has some of the best submissions GnP and transitions in the HW division, which on the ground in mma gives him an edge against anyone. His stand-up skills have beaten k-1 level strikers, and his sambo is just unorthodox enough that even fighters with great
sprawls get taken down because sprawls dont matter in the clinch.
He can beat 99% of fighters standing, 99% of fighters on the ground, and can take most fighters down effectively.
The only Style type that can beat him IMO(other than by a perfect punch/kick) is a master Bjj fighter with Great takedowns.... the closest example of this would be Ricardo Arona if he was naturally just a wee bit bigger.
Anderson silva is less complete of a fighter IMO, what if he ends up facing someone whos a better striker? as unlikely as it might seem, what does he do then if said fighter has above average takedown defense, andersons ability to take it to the ground isnt nearly as strong as fedors, nor is his submission game. So while his striking is deadly and awe inspiring, hes not near as complete as fedor is.
I could give a breakdown for each fighter on my list but it just seems like more typing than im willing to do right now