I've been more hardcore about boxing and been following MMA since 2010 and in my opinion GSP is the greatest MMA fighter I've seen however I've never understood why Fedor is considered to be GOAT by so many. Looking at his resume... it doesn't look that impressive, he hasn't got a single win over an elite fighter.
Cro Cop arguably his best win... he got absolute destroyed in the UFC, true that he went to the UFC when he was 32 but fighters in the higher weights are usually able to maintain their prime into 36-37. Cro Cop who got beat by Mark Hunt who was completely average in the UFC as well.
Big Nog... same thing, joined the UFC at the age of 30/31... definition of prime age and also got dismantled by everyone.
Fedor beat... what it seems like to me, mostly average fighters, none of them have any distinct achievements and fought when MMA was still fresh and very underdeveloped.
Please I'd love to be educated as to why.
He was the best of his day. That's typically what people mean by GOAT. Why is Babe Ruth considered one of the baseball GOAT's? Why is Jesse Owens (his times are slow by today's standards) one of the sprinting GOAT's? Why is Mark Spitz (again, times slow compared to today) considered one of the swimming GOAT's?
And its not just in sport. The Roman Legions would be wiped out by even a small modern army, but they are considered one of the GOAT armies. Galileo's knowledge of physics is less than any modern high school science student, but he's considered one of the physics and science GOAT's.
GOAT is almost always compared in terms of how you did against the best of your day. Fedor was the best of his day at HW (unless you think the UFC, whose HW champs were Arlovski and Tim Sylvia, had better HW's than him), and for many people HW is the most prestigious weight division, since they'd still be champs even if there were no weight divisions (MMA, like boxing, wrestling, judo, and BJJ started without weight divisions, they're pretty artificial).
The age thing is always interesting. On Sherdog people seem to think there's a standard age for when someone is at their peak. That is, they think everyone ages at the same rate. That's pretty odd, even when you ignore things like injuries and wear and tear from accumulation of fights (especially training, since, in MMA most wear and tear comes from training rather than actual fights). You need only go to an old folks home to see 90 year olds who are in better shape than some 60 year olds. Or talk to a doctor, who will tell you of people who die of natural causes at the age of 30, and other people who live well into their 100's -- everyone aging at the same rate is simply false. How so many Sherdoggers don't get this I don't know, its one of the most obvious things about humans -- we age very differently.