Longest title defense reign vs quality opposition : GSP
Quality opposition ? The quality of the opposition is up for debate, you can make cases for Jones, DC, Anderson and Fedor.
Mighty Mouse and Anderson Silva had more consecutive title defenses. Mighty Mouses' is ongoing, with a match up against TJ next he could start showcasing his p4p greatness against a great fighter and champion in the division above. (unlike Bisping who was a weak champion)
Fedor had the longest undefeated reign.
Jon Jones has never truly been beaten.
DC has only ever lost against a PED using Jon Jones. He has success in two divisions, he's fighting against the longest reigning UFC HW champion ever (3 consecutive defenses) in Stipe. Should he win his case will be getting stronger.
Biggest selling PPV star : GSP
That's got nothing to do with success inside the octagon or fighting skills.
Only fighter to ever avenge all his loses : GSP
That's a good point, but Jon Jones hasn't properly lost.
DC has only ever lost to a PED using Jones.
Longest streak without ever losing a round : GSP
Many would consider finishing streaks to be better. Jon Jones came to the UFC and finished 8 of his first 9 opponents. Including finishes over the likes of Shogun, Rampage, Machida, Vitor and Chael.
Anderson finished his first 8 UFC opponents.
Whens the last time Mighty Mouse lost a round ?
Only fighter to win 2 belts in different weight classes : GSP
DC won the SF HW Grand Prix and is the reigning UFC LHW champion, he's fighting for the UFC HW title next. Should he beat Stipe his two division exploits will shit all over GSPs.
Conor McGregor.
Andersons exploits at LHW were just as good as GSPs at MW. (seeing as GSP only fought and beat Michael Bisping)
Only fighter to not test positive or get his ass kicked repeatedly ever since testing became the norm : GSP
He came back for
one fight during the USADA era. Had he came back, won the title, defended it against the likes of Yoel, Rockhold and co it would have been impressive, but alas, he left the UFC, came back to fight once (in a cherry picked fight) and is now gone again. His last fight before leaving was a controversial victory over Hendricks. Many feel he lost that fight.
Just because he hasn't tested positive doesn't mean he's totally clean. In fact, many will argue till the sun goes down that he has took PEDs in his career.
DC has only ever lost to a PED using GOAT candidate.
Mighty Mouse is reigning long and hard through this USADA era.
All in all GSP is one of the GOATs and you can argue him for #1. But to say he is undisputed #1 is a lie. Their is plenty of room for debate.