I think it is most likely to be Hashirama because he could control the Tailed Beasts and he defeated Madara with his Eternal Mangekyou Sharingan and which is something i can't really see the other Kages doing

It wouldn't surprise me if he actually were the most powerful Kage in history. People raigned and hailed him as the God of Shinobi. Only Rikoudu Sennin had yet aquired that title. That means something. I'd say Onoki, Mei, A, and Hashirama are also good contestants.

in my opinion i think he is the strongest kage. why, who do you think can beat both the first and second hokage at the same time and had severely injured orichimaru in the process, not to mention he did it while he is way beyond his prime, now thats is a sign of a really strong kage.

Well thats what they said.

he was the 1 one so i picked him

Hashirama dealed with both kurama and madara , now that is some serious fight