Sylvia was still good when he fought Fedor but he was definitely past his best days. With that said he was still good enough to heat beat the likes of Brandon Vera. Out of Big Nog, Coo and AA, Tim was the least in his prime but the way Fedor annihilated him was impressive and unprecedented.
AA at his peak was an absolute animal and had the power and speed to KO literally anyone. He was on a tear when Fedor swatted him out of the sky. Coming into that fight with wins over Werdum and stoppages over Rothwell and Nelson who no one was stopping in those days. Not even prime JDS. AA was training with Freddie Roach at the time and sparring Andy Ruiz every day.
Just because AA has been KOd doesn't mean a win over him at his very best means nothing.