Bones and GSP are GOAT level for sure.
GSP took 2 Ls, but came back and avenged those losses then went up, got the middle weight strap, and retired on top
Khabib undefeated and retired on top, but didn't have as long a run of title defenses as GSP and Bones.
For Izzy, I just don't want to see him losing sad the way Anderson Silva ended his career.