I think GSP is the GOAT, even if he didn't move up to win the MW belt. His overall resume of top 10 & top 5 wins, title defenses, not failed PED tests, avenged all his losses, retired as champ. Having said that, I have a hard time believing it.
Like when Anderson was champ, GSP tried to convince people Anderson was 45 lbs bigger than him. GSP even at 195, is in great shape, with no excess body fat. He has a habit of bringing up other peoples walk around weight as evidence he's at a disadvantage, but Anderson at 45 lbs bigger than GSP is not in fight shape. I think GSP would've beat Anderson BTW, he would've Chael'd him except not get subbed. Khabib at 195 lbs does not look like GSP, GSP is a bit disingenuous when he suggests Khabib is bigger or as big as him by talking about Khabib's walk around weight. Khabib at his 155 weigh in, does not look as ripped/shredded as GSP at his 170 weigh in.