I don't think the HoF should include all title holders, it should be a bit more exclusive than that. It should also only include retired fighters. In a sport this young, I wouldn't go with the 5 years retired thing like the NFL has yet. Off the top of my head, and in no particular order, I would put in:
Royce Gracie
Randy Couture
Matt Hughes
Chuck Liddell
Tim Sylvia - Like him or not, he was the most dominant HW champ until Stipe.
Tito Ortiz
Rich Franklin - Probably wouldn't have a lot of success in today's MW division, but he was a dominant champ and holds a win over Liddell.
Forrest Griffin - Due to significance rather than greatness. I'd give him the nod but not Bonnar because Griffin was a champion.
GSP - If he stays retired
Ronda Rousey - Don't let how it ended obscure how great her career was.
BJ Penn - His record isn't great, but he had a pretty damned dominant run at lightweight, as well as beating Hughes for the title at Welterweight.
I've probably missed a few, and I left out anyone still active. Among active fighters I believe belong as soon as they retire I would have:
Anderson Silva
Jose Aldo
Demetrious Johnson
Jon Jones
Dominic Cruz
Stipe Miocic
Joanna Jedrzeczyk
Ones I would have on the cusp, either needing a bit more, or maybe making it as is:
Robbie Lawler
Conor McGregor
TJ Dillashaw
Khabib Nurmagomedov
Tony Ferguson
Max Holloway
Michael Bisping
Cain Velasquez
Frank Mir
Again, I am sure I am missing some, especially from the early days. I left out guys whose greatest accomplishments were in other organizations, such as Antonio Rodrigo Nogueira.
