If every fighter was the same weight and gender, who would be the best fighter. This is how P4P is supposed to work, but it relies more on legacy and win streaks. However, what if that was ignored and the list was simply based on who beats whom.
My list is probably way off so feel free to critique.
1. Dominic Cruz. In my opinion, he beats anyone they put in front of him with a full camp. One of the smartest fighters out there and constantly adjusts round by round.
2. Jon Jones. I have been following Cormier since his entire career. After I saw the Gus fight, I knew Cormier would trash Jones. As did Cormier. However, Jones just gets better and better after every fight and always rises to the occasion. The Jones that fought Gus would have been trashed by comrier. Yet he put his mind to it and was able to defeat a guy many thought he couldn't. This guy is not only elite, but he has new tools everytime he gets in the cage.
3. Khabib N. This guy trashes 99 percent of the UFC roster. RDA is just holding his belt.
4. Daniel Cormier. Went 5 rounds with arguably the best fighter to have ever lived with one of the worst reach disadvantages in any fight. A shame he didn't get into mma when he was younger, doesn't get the credit he deserves.
5. Connor McGregor. Yes, chad got 2 weeks notice. But this is not as big as a deal as people seem to think. Fighters fight and WIN on two weeks notice all the time. Cerrone does it like twice a week. If you get 2 weeks, it doesn't automatically mean you are going to lose. Especially, when everyone in the world thinks he was going to demolish the joker that he was fighting. Additionally, Conor did not wrestle at all during the camp, was not trained for Mendes, and fought with a torn MCL. Yes, the 2 weeks makes a difference. But it doesn't discredit this win. That being said, Chad was a way worse matchup than Aldo for Conor. If he can beat Chad, there are not many people I see him losing to. Khabib, Cruz, Uriah and Frankie are the only guys I can think of.
Honorable mentions: Rousey, Jose Aldo, Frankie Edgar, Mighty Mouse. 
In no order
Rousey (as much as it pains me to say)
Werdum
Jones
Cormier
DJ 
Someonestolemysocks - In no orderHigh altitude Werdum can join my honorable mentions.
Rousey (as much as it pains me to say)
Werdum
Jones
Cormier
DJ
Jones
Aldo
DJ
Rousey
Weidman
Cruz
Werdum
Weidman and Rockhold
Mighty Mouse
Can't think of anyone to put at five. Too many to consider lol.
Libero21 - JonesI voted you up purely because I have always had Mitsubishi Liberos lol.
Aldo
DJ
Rousey
Weidman
Jones shouldn't be on there. If it's based solely on skill, he is definitely pretty high up the ladder, but so much of what he does and is able to do is because of his length. He uses his size better than anyone in the history of the UFC and is a couple of years of fights away from being the unquestionable GOAT, but on a P4P scale weighing only skill and assuming all combatants have the same size and reach, he doesn't really belong.
" Conor for his striking. Hes MMA's first real striking savant plus he has shoen he can beat the best wrestlers"
Did you literally just start watching mma this month?
Naughty Gorilla - " Conor for his striking. Hes MMA's first real striking savant plus he has shoen he can beat the best wrestlers"This ^
Did you literally just start watching mma this month?
Jones gets added to the list simply because he beats everyone you put in front of him. He defies all logic. His skill set isn't in the top 5. However, he beats fighters who have those skill sets. It's an anomaly of all sorts, but you can't just say he isn't in the top 5 p4p because it is not quantifiable. I know I said it's based on skill, but beating everyone is kinda a skill.
Dylan, Dylan, Dylan, Dylan and Dylan.
He spits hot fire.
Naughty Gorilla - " Conor for his striking. Hes MMA's first real striking savant plus he has shoen he can beat the best wrestlers"Pretty sure he did.
Did you literally just start watching mma this month?
Also a bad troll.
No joanna champion? 6 time muay thai world champ. Only 115 lb girl but still drops people... She has to be up there. - the ufc doesnt have anyone else like this
Southpaw76 - No joanna champion? 6 time muay thai world champ. Only 115 lb girl but still drops people... She has to be up there. - the ufc doesnt have anyone else like thisDon't hate the idea.
Forget about quick submission wins and what not...p4p, Joanna has been consistently fucking up her peers more than any one else so far.
The Pendulum -Dj and Aldo came to mind immediately.. VULibero21 - JonesI voted you up purely because I have always had Mitsubishi Liberos lol.
Aldo
DJ
Rousey
Weidman
I love Conor, but btfos is a fucking embarrassment.
The shit he comes up with is so bad, I have to assume he is actually a Conor hater who is trying to act like a fan in order to turn people against him.