Who would win in a one-on-one? Most
definitely Gothmog.
Sauron's "greatness" and his being the second in command after
Melkor,(which seems to be coming up constantly, and used as an argument for Sauron's sake) has NOTHING (or very little) to do with his prowess as a warrior. His greatness lay in his cunning, his magnificent skill as a craftsman/smith, his superior will, his dark sorcery.
Was Sauron ever sent to one of the great
battles? No. Why is that?
Because fighting as such is simply not his "thing". He will resort to coming forth himself
only at uttermost need, when all else fails.
Remember Tol-in-Gaurhoth? Sauron ruled from behind the scenes, sending werewolves to destroy his enemies. Finally, when all were defeated, he appeared himself, and got his butt whopped by a girl and her doggie.
Remember the
Battle of Dagorlad? After a battle of immense proportions and the loss of many on both sides, Sauron
retreated to
Barad-dur and resisted a 7-YEAR-LONG siege, ruling from the inside of his mighty
fortress (which was a great achievement of his, as a
Maia of
Aulë, and a display of one of his greatest skills and powers), using his power through his servants, rather than facing his opponents himself. When he finally emerged from the
Dark Tower, he was defeated. He failed as a warrior, his bodily form was destroyed, but the greatness of his will lived on through his marvellous creation,
the One Ring.
Remember the
War of the Ring? Especially the Battle of the
Morannon. Why wasn't Sauron there to personally deal with his chief foes...to take pleasure in the slaying of the likes of
Mithrandir and
Aragorn? His eye was directed at the battlefield, the strength of his will uplifting the spirit of his minions and filling the hearts of his enemies with despair and fear.
Quite on the contrary,
Gothmog's greatness lay mainly in his warrior skills, in his deadly
weapons (whips of fire), and the terror that went before him. He and the other
Valaraukar were always present on the battlefields and were terrible foes.
So there - the answer to your query is more than obvious.
