Not at all downgrading Khabib. He is a phenomenal fighter, and I was hoping we got to see the next Fedor. I am surprised every time I see him, at how dominant he is.
However, he is a very big guy, that struggle to make lw. GSP was also a pretty big weightcutter (if I am not mistaken, even if he never failed weight), so they both probably had this advantages in most fights. GSP fighting the MW champ was an impressive feat, even if he had beat Bisping in practice. I would like to see how Khabib does when undersized. That is what all the greats do.