Obama is #1 - THE GREATEST PRESIDENT IN U.S. HISTORY. PERIOD.
FDR comes in 2nd place.
Slaveholders do not make the list. Those that did not vow to destroy the KKK domestic terrorist group or to abolish the Black Codes, segregation, guarantee the right to vote for all citizens, and put and end to Jim Crow Laws are automatically put at THE BOTTOM of the list of the greatest presidents as well.
Pepole like andre dont even call him the greatest in history, and maintain a straight face.
Slave ownership or the lack of desire to abolish it don't have anything to do with poor leadership qualities, given the time period. In fact, if we look at the direction/organization involved in it, it might require a better leader. You are just sour because you happen to be black and it gives you something to cry about and excuses for your short comings.
Many would view hitler as 1 of the greatest leaders the world has ever seen, given what he was able to accomplish and his ability to rule. That's not to say he wasn't a twisted psycho with evil motives, but those things are really separate issues.