People need to stop thinking of the titles and think of what they can actually do, when you do think like that you will clearly see that the dragonborn can kill those 2 in just a few sec, simple because dragon shouts > everything
ROFLMAO no. Dragonborn = dragon killer, Nerevarine = God killer, Champion of Cyrodiil = eventually a God. From those descriptions, I would say that the Nerevarine would beat the Champion, and the Champion would beat the Dragonborn. Plus, no one knows what happened to the Nerevarine, except that he went to Akavir. For all we know, he encountered a force that made him even more powerful, or perhaps killed him. The lore isn't specific enough for an actual comparison of the characters, because much of what happens after the game is unknown.
And as far as the game mechanics goes, the Nerevarine would DEFINITELY win there, so I see why that isn't part of the vote.