Conor would probably rank for me somewhere around the 15th-20th best MMA fighter of all time.
Captured belts in 2 weight divisions, and had an incredible run. But the big knock is that he never defended either title.
Tier 1 - GSP, Fedor, Jones, Silva, Mighty Mouse, Khabib
Tier 2 - DC, Hughes, Aldo, Big Nog, Cejudo
Tier 3 - Couture, Penn, Cruz, Lawler, Hendo
Tier 4 - This is where Conor might fall in
DC there but no current HW champ ??