The problem with calling Hendo the G.O.A.T. is that he has lost too many KEY fights. Probably lost as many big ones as he has won.
That versus what guys like Fedor, GSP and Anderson have done makes it hard to give Hendo that title. Hendo has also always had glaring holes in his game that people have exposed a lot of times (cardio, submission defense, take down defense).
Is he one of the best fighters this sport has ever, and probably will ever, see? Absolutely.