Upon much thinking about ranking warriors of Spartacus it comes to the age old debate about who is the better warrior Spartacus or Gannicus. Now I think they stand equal but only because they are Gods on their respective fronts. Gannicus was the god of the arena and as someone stated had an uncanny ability to win fights even when losing. Caburus superior in strength smashed Gannicus around and almost killed Crixus. Gannicus enters his rage mode and pulls an excellent counter tearing most of his jaw off. Knocked to the ground by The Egyptian and sees Oenomaus fatally wounded and kill him easily within 20 seconds. Gannicus in his prime in Gods of the arena was the god of the arena and that was as Batiatus described as his "Olympus." Spartacus is an equally devestating warrior on his "Olympus"/ his front which is the battlefield. Wields an array of weapons with deadly purpose with his military and strategic mind makes him a fearsome foe in his prime in War of the damned. They never faced each other in their primes an not on their particular fronts so I think in my opinion it is fair to say they stand equal but specialize in their home grounds.
I hope you can agree/