Abraham Lincoln, George Washington and Franklin D. Roosevelt were ranked as the top three US presidents in history respectively while Barack Obama entered the rankings in the 12th spot, based on a survey of historians released on Friday.Theodore Roosevelt and Dwight Eisenhower rounded out the top five of 43 presidents in US history, a survey of historians' rankings of presidential leadership found.It was the third such survey released by the C-SPAN television network ahead of the Presidents Day weekend."Once again the big three are Lincoln, Washington and FDR - as it should be. That Obama came in at number 12 his first time out is quite impressive," said Douglas Brinkley, a history professor at Rice University, in a statement by C-SPAN.The survey, which was held twice before in 2000 and 2009, asked 91 presidential historians to rank the 43 former presidents based on 10 attributes of leadership.Obama, who left office in January with favorable approval ratings after serving eight years, was ranked third in the "pursued equal justice of all" category and 39th in the "relations with congress" category."One would have thought that former President Obama’s favorable rating when he left office would have translated into a higher ranking," said Edna Greene Medford, a history professor at Howard University. "But, of course, historians prefer to view the past from a distance, and only time will reveal his legacy."Andrew Johnson, Franklin Pierce and James Buchanan were ranked as the worst presidents in US history, even lower than William Henry Harrison, who served for only one month.