The 4th was great, but I put him at 2. In addition to stating your result, it'd be great to give a brief reason.
1st)
Think about all the 1st did:
-Establish Konoha/end warring in that nation
-Defeat Madara
-Wood Kekkei Genkei
-Started the greatest lineage of student-teacher ever:
-1st->3rd->Jiraiya->Minato (also Naruto)->Kakashi->Naruto
-(Other stuff I forgot)
Minato(4th):
Minato did father Naruto, but then in theory half the credit goes to Kushina. Everyone knows the great things he's done, so I won't go into it with depth.
-{Reaper death seal, which saved Konoha twice since Sarutobi used it on Orochimaru},
-{Rasengan, ultimate in spatial recomposition, now FRS with Naruto}
-{Flash space-time jutsu that gave him his name where he could eliminate 50 (I believe it was 50 in the Kakashi Gaiden men without a scratch}.
-*I know Madara saw through everything, but it couldn't have been everything since the 4th sealed the Kyuubi on him.
-As above: Minato->Kakashi->Naruto
If Jiraiya had accepted, I think he may have been stronger than the third, but that's oooooooohhhh "speculation", "conjecture", or taboo thinking these days it seems.
Tsunade:
Don't hate on Tsunade even though I have her low. I don't think we ever saw how powerful she really was. We know that she was the greatest medical ninja ever (Kabuto is probably second though Sakura is coming around). She really did "gamble it all" using that Katsuyu jutsu to heal everyone alive depleting all of her chakra. She also oversaw the rebuilding of Konoha after Orochimaru trashed the place. She was a Sannin for a reason, it's not like Hanzo named her one out of pity.
Edit: The 6th is pending. I know nothing about Danzou other than that he's a bastard manipulator. He trained at the same time as the third and vied for Hokage at multiple times. He's not weak, but I think he's probably a chump compared to Kakashi, whom I would insert between the 3rd and 5th. Hokage are supposed to risk their lives to protect the village, Danzou uses pawns to protect himself. I sure as hell hope Sasuke use Tsukiyomi on him.
Regarding the third: He was a badass, but I'm not qualified compared to others to speak on his behalf, same with the 2nd.
My rankings:
-1st
-4th
-3rd
-6th (If and only if (iff) it's Kakashi and not Danzou {whom I consider interim} )
-5th
-2nd (I really don't know much about him other than his unparralled water jutsu)
Obviously when all is said and done, Naruto is number one, but not yet.