Well, according to the manga, Hashirama when he was alive was stronger than anyone who's alive right now (stated when DSM Kabuto was still in his prime, BM Naruto, EMS Sasuke, and Obito were alive). It's stated twice that the combined efforts of the Five Kage are nothing compared to Hashirama.
SO6P, he's on another level. Kurama still believes that he's above Edo Madara (he said that he's above everyone), and that's after he wasn't the Juubi's jinchuuriki anymore and was in old age (Kurama was created after the Juubi was split up into the nine biju, duh). So, yeah.
Hiruzen, he's under both of them but still good in his own right.