Hashirmama is considered a god among shinobi; alone he dueled and defeated Madara Uchiha and the Kyuubi, a feat that the current five kage together couldn't accomplish.
... that said, Toneri Otsutski in possession of the Tenseigan is a force to be reckoned with, evidenced by the fact that Naruto saw fit to enter one of his strongest forms to counter the threat.
With all of their greatest jutsu and skills in mind, I ask: who would win?
My personal vote, with Hashirama's Bringer of Darkness genjutsu, Sage Mode enhancements, and Wood Release mastery in mind, is the First Hokage. What do you guys think?