I don't know about the best...but my favorite is by far Teddy Roosevelt. One of the first leaders of the Progressive movement, who believed that the government could be used to balance the playing field, eliminate monopolies, and in the end raise the quality of life for the poor to an acceptable level. We need more people like Teddy Roosevelt to run for President today, I think (as in an anti-corporatist who looks out for the people...sort of like Ralph Nader
).
While it's true that WW2 is actually what brought the country out of the Great Depression, FDR's social programs at least gave people something to hold onto, whereas Hoover believed in "letting things work themselves out". FDR was a good President, but things like the Japanese WW2 internment camps prevent me from liking him much overall.
Edit: Listage-
Best:
1. Teddy Roosevelt
2. George Washington
3. Abe Lincoln
4. FDR
I don't know enough about obscure Presidents to know who the worst is.