The question who was the best and already there are two excellent choices. If I was compiling a list of the top 5 presidents Lincoln and Truman would be on my list.
So, I will offer another candidate. Thomas Jefferson doubled the size of the nation with the Louisiana Purchase. The Monroe Doctrine, which stated that North America was no longer open to colonization by other countries came later. If Jefferson had not approved the Louisiana Purchase, there is no telling which country would be occupying that vast area west of the Mississippi River. He had other less famous accomplishments, but is certainly worthy of being considered as the best. However, comparing presidents from four different centuries is extremely difficult.
George Washington is said to have invented the presidency and Andrew Jackson is said to have reinvented it. FDR also deserves consideration for creating Social Security and for creating federally funded jobs during the Great Depression.