My thread supports what KingHashirama is saying.
Hashirama is the most powerful Hokage. Period.
Edo Madara fodderizes the five current Kage:
Edo Madara states the only one who can stop him is Hashirama:
Edo Madara states that Tsunade's medical ninjutsu is worthless in comparison to Hashirama's:
Edo Madara explains just how outclassed Tsunade was by her grandfather:
Edo Madara states that the five Kage together are nothing compared to Hashirama:
Edo Madara states that only he with his EMS could see through Hashirama's mokuton clone jutsu:
Dan shouldn't count, but he says the only one who can beat Edo Madara is Hashirama:
Madara must have known about Hiruzen and Minato because these guys gathered information for him; it's not as if he wasn't up-to-date with everything:
Hashirama is superior to Tobirama (as much as I hate to say it):
So, Edo Madara was shown to fodderize Tsunade (along with four other Kage), and Hashirama is shown to be superior to Tobirama (this is obvious, sadly), Hiruzen, and Minato through statements by Edo Madara (and Dan, who once again, shouldn't count).