7-0 against UFC HW champs. Come on. Of course he's elite. Best ever? It's hard to say that. Ain't a pony can't be rode, ain't a cowboy can't be throwed.
It's a high stake game of inches. He got clipped a few times, it's bound to happen with that style where you wade in, and it's MMA. In boxing you have a few undefeated champions, but you have time to recover after a knockdown, a luxury not granted in MMA. The only high level HW boxer I know of that was never dropped is George Chuvalo, but he was still TKOd two or three times. Ali, Lewis, Louis, Foreman, Marciano, Tyson, Frasier, Fury, all have been dropped multiple times. If that were MMA, you get jumped on and pounded, probably out. So losses in MMA are more forgivable. Shit happens. It doesn't take away from greatness.
As far as the greatest of all time? That's something that exists only in the mind of fans. We idolize, because if another mere man can be seemingly immortal, then maybe we can too.
But at the end of the day, Fedor is just another person, with the same Oxygen, Hydrogen, Nitrogen, and Carbon molecules making up his body as mine, yours, and the thread starter's. Nothing too special at the end of the day, just a monkey that learned to talk, do a couple judo throws, and wing a couple punches.