Board Thread:Naruto Discussions/@comment-27202380-20151124031155/@comment-734582-20151124095123

Legendary Super Saiya-Jin 4 wrote: Third Raikage was stated to be the greatest Raikage that Kumogakure ever had, so he was likely the strongest. As for all the other First Kage, all we can assume is that they were all pretty strong since they lived in Hashirama and Madara's era. The Third Raikage and Kazekage were said to be the strongest of their respective villages, so it's safe to assume they are. However, as you said, the first Kages seem to have been among the strongest, mostly because of continuous battle experience in their never-ending war.