He definitely is 1 of the best current fighters and may ultimately finish his career as 1 of the best ever but imo he's not even in the discussion as the best P4P ever. He has got an outstanding unbeaten record obviously but you don't have to look into to hard to realize that he fought a lot of scrubs early on which makes up over half his resume,even his UFC record has more fringe contenders on it then it does rated guys. He needs more title defenses and some sustained success at the top to even be considered the best in his division,since his 1st big win over DosAnjos back in 2014 he's only been averaging 1 fight a year
As of right now he is nowhere near the title of p4p greatest. He hasn't proven he is the best current lightweight fighter let alone the best p4p fighter in history. Lets have this discussion in another 6/7/8 years or so and see how his career pans out.
Even though Khabib is 27-0, let's face it, those wins weren't against the most rigorous opponents: Pat Healy, Darrell Horcher, Thiago Tavares etc. I'm not saying Khabib is afraid of the best. He's shown he's not afraid of anybody. But aside from wins over RDA and Conor his resume is pretty sparse. He's got a lot of work ahead of him to even be in the GOAT discussion. If he beats Poirier and Ferguson back to back that would get him a lot closer. If he defended against Gaethje that'd help, and jumping to 170 and claiming a title there on top of all that would really get him in the mix with GSP and Jon Jones.
PFP one of the strongest men ever to step-in.. Crazy, Matt Hughes-like gorilla strength, but not a GOAT. Not yet
Got to have the greatest ground game I've seen in UFC. Other areas he hasn't shown much in (hasn't been forced to). I dislike religious bigots, but the man is a hell of a wrestler.