We havn't really seen much from either of the hokages. Im leaning towards the third hokage for now because of the things iruka, kabuto and orochimaru said. Iruka said he was the strongest hokage ever and kabuto said that he was the strongest kage of his generation, meaning he's stronger than the third kazekage (strongest kazekage ever + iron sand), third tsuchikage (the dust user with the back problems) and the third raikage (the one who was defeated by his own attack). Orochimaru said he was known as the god of shinobi and knew and could use all the justsu which existed in konoha, except kekkei genkai of course.
Hashirama DID fight madara (pre rinnegan) but I think madara made one big mistake - using the 9 tails. Hashirama could have just taken over it using his wood techniques and used it against madara which is what I think happened.
Thanks.
