Fedor beat three K-1 World Champions (Cro Cop, Semmy Schilt, Hunt)
Fedor beat two ADCC World Champions (Jeff Monson & Ricardo Arona)
Fedor beat two Judo World Champions (Satoshi Ishii & Naoya Ogawa)
Fedor beat 7 UFC champions (Nog, Randleman, Coleman, Arlovski, Sylvia, Rampage, Mir)
Of those UFC champions, he beat two of them twice.
Fedor has proved that he can stand in front of either the best kickboxers of all time, the best grapplers of all time, and the best MMA fighters of all time and he will still beat them.
MMA was basically still in its childhood stage, but Fedor was the GOAT of that period. You can't always compare him to current fighters, as the sport was still in early form of its evolution.