[Morthoron]

To elaborate on what other posters have said, particularly Mith and Legate, I think if you are going to make comparative assumptions regarding an army plopped into another Age of Middle-earth, it must be done in context, and with the baggage train they carried.

For instance, if you are speaking of a Numenorean army, which one precisely? If you are referring to the armada of Ar-Pharazon, I believe it would be likely that they would have already been seduced by Morgoth and turn on the Elves. Remember, many of them already worshipped in the cult of Morgoth. Beyond that, the corruptibility of Men is well documented throughout Tolkien's corpus. And as others have stated, Morgoth had an eternity to work his wiles.

But aside from context, in reality, no Numenorean army would do anything but delay the inevitable victory of Morgoth as pronounced in the Doom of Mandos. It was a no-win situation. Defeat was ordained. And really, the Edain that fought against Morgoth were if anything just as powerful a force as the Numenoreans. They were their ancestors, after all.