Hashirama and Madara started the village but Hashirama did not really know what to do with it once his dream of the village was accomplished. Tobirama was the best Hokage. He set up most of the systems and infrastructure that still exist in the village today. The Academy, the Chunin Exams, ANBU, and the Police Force were all set up under Tobirama. The Academy helped to prolong the life of the villages children and better prepare them for life as ninja.
Hiruzen was good at training shinobi and keeping the continuity with what Tobirama had set up. Minato died too early after he became Hokage to have many accomplishments as such. Tsunade is still Hokage so to judge her time as Hokage is premature.
The first three Hokage were all called God of Shinobi. But as far as accomplishments as Hokage I would have to say Tobirama did more to set the village on the right path than any of the others.