It is probably safest to assume that the most successful president was Abraham Lincoln, with George Washington a close second.
However, the American Political Science Association were highly agreed in selecting Roosevelt as best president. There have been other good and well-meaning presidents such as Obama, but they have not been successful on the world state in respect of good outcomes of their interventions.
This is of course a question that asks an opinion so you may want to disagree with me but I think Barack Obama is the most successful United States President of all time. Interestingly, C-SPAN’s third Presidential Historians Survey ranked Obama 12th overall, which they said is quite impressive given it was his first time under consideration.
C-SPAN’s survey rates presidents on ten qualities: public persuasion, crisis leadership, economic management, moral authority, international relations, administrative skills, relations with Congress, vision, pursued equal justice for all, and performance within the context of his times. For me, the fact that President Obama led us out of the economic crisis and never had one scandal during his two terms in office make him the winner.