The Manga clearly states that Hiruzen was the strongest Hokage during his prime. The reason you people don't want to believe that is because if Hiruzen is stronger than Hashirama, then that is very likely to make him stronger than Madara as well. Madara himself admitted that Hashirama was still able to defeat him.
You people think that his Susano'o is invincible, though Hashirama was still able to defeat it. Uchihas are not the only ones with great power and techniques. Hashirama was also a direct descendant of the SO6P; he must also have very strong techs. Just because we have never seen all of his techs, does not that he doesn't have one more powerful than Susano'o.
The same goes for Hiruzen. Just because he's not an Uchiha or never showed powerful techs, does not mean that he doesn't have something powerful do defeat Hashirama or Madara.
It baffles me on how closed-minded and stupid you people really are. For god sakes... just ****ing think and stop acting like ****ing babies!