Lets see all kage powers at there best and now :
First hashirama : wood style ( means already 2 nature type earth and water ) a kekkei genkai . At a level to Defeated a susano .god of shinobi . Capture all tailed beasts ....
Secound tobirama : strongest water user and master of creating jutus . So much i would be out of ink writing them ....
Third sarutobi : he knows 5 nature element user ( not enaught to combine but still ) summoning a monkey and ....
Forth minato : invented rassengan flying space time jutsu .and after reanimated 9 tails chakra control ...
Fifth tsunade : i think she is secound weakest after kakashi but she is a medical shinobi so diffrent prespective yet she is a legendary sanin summon giant slug healing and master that mark on her head.
Six kakashi : know 2 nature jutsu (electric and earth but not at a level to combine them kekkei genkai) summons dogs ... And the peak of his power isnt original his the sharigan (but lets add it ) he reach susano and kamui ability , that at his max power where he reach it for only like 1 minute of susano . And lets see his power now whithout sharingan ( he said kakashi of the sharigan is no more ) where does that put him ? Yes he is strong (but there is many stronger exemple 7 gate might gai ) Yes he is a assassin and a ambu (yamato was also and he knows wood style ).the only good qualifications for picking him that he already knows the villages dark secrets the most.
Seven naruto : we all know but lets mention some . Sage mode , rassengan .wind style . 9 tails mode ...
(When i put .... i mean other basic jutsus and shinobi stuff like shadow clone shuriken shit etc... it is school shit every shinobi know it )