The following is my thoughts on various parts of the list, being somewhat of an amateur historian.
It is funny to see where presidents end up ranking historically. Lincoln, Truman, and JFK were considered failures at the times they were in office. Truman had even been written off in the 1948 elections as having lost to Governor Dewey.
JFK was losing his re-election bid, forced to fly to Dallas to save Texas for the Democrats despite having native son Lyndon Johnson on the ballot with him. That trip, of course, was his last as he was killed in Dallas. JFK was the original conservative supply-sider, successfully reducing the top tax rate from 92% to 70%. But he's also responsible for the Bay of Pigs and US entry into Vietnam, though on the plus side of his ledger is the Cuban Missile Crisis. i expect as more time passes, JFK's ranking will drop as his assassination plus this nation's fascination with Camelot will fade eventually.
Frankly, I'm surprised to see Bush 41 rated as high as he is, placing 18'th on the list. He was considered a failure, having presided over the "worst economy of the last 50 years." He did free Kuwait, for which he earns most of his consideration.
I have observed, that with the singular exception of the Great Depression, economics really plays no role in a president's historical standing. Economies come and go despite presidents, usually, and history reflects that. No matter your opinion on Bush 43's handling of the economy, in thirty years, nobody's going to care, so it won't even play a role.
Ironically, the Great Depression somehow enhanced Roosevelt's standing, despite having enacted policies that historians now consider to have lengthened and deepened the Depression. I will give him top marks for his political handling of the Allied powers up until US entry into WWII and for his handling of the war itself. Without the Great Depression, I would have ranked FDR #3. With it, I would place him close to the middle of the pack as far too many of his negative economic policies are still with us today.
Note that Calvin Coolidge presided over the Roaring 20's, one of the biggest periods of prosperity this country has ever seen. Yet despite that, he is ranked #26, which goes to show how little economics usually matters.
Eisenhower was eighth on the list, again a major surprise. Eisenhower was personally popular, having been a hero during WWII, but was a disaster for his own party, presiding over some of the biggest Republican losses in electoral history. Personally, I liked Ike but his presidency wasn't much to note. His, like Bill Clinton's, was primarily a do-nothing presidency.
Another huge surprise is Lyndon Johnson, widely considered incompetent for having badly botched the Vietnam War and leaving office in disgrace. I suppose the Great Society is responsible for some of his popularity, but the GS is now widely considered a $6 trillion failure, having done nothing to actually solve poverty.
Woodrow Wilson is another surprise at #9. While he did preside over victory in WWI, he was primarily responsible for botching the aftermath of the war. Extreme punitive measures against the Axis powers, and Germany in particular, plus his weakening of US and international resolve led to disarmament on the part of the Allies and the rise of Adolf Hitler. If he had acted differently, perhaps 50 million people wouldn't have died in WWII.
John Adams, I think, should rate much higher as he successfully avoided a war with France that his country could ill afford at the time, still recovering from the American Revolution.
I would have placed Thomas Jefferson as #3 overall on this list, much of it for his foreign policy in his handling of the Barbary pirates and the Louisiana Purchase.
Though I'm a great fan of US Grant, placing him 23'rd on the list is a travesty. His was an administration wracked with scandal, though he himself was untouched by it personally. The scandals made him ineffective, leaving Grant to say about himself that he wasn't up to the job.
I do have to agree with the assessments of Andrew Johnson and James Buchanan. Buchanan did nothing to bring the country together when it was on the verge of civil war, leaving all the heavy lifting to his successor, Abraham Lincoln. Lincoln's successor was arguably worse in the aftermath of the Civil War, with the only accomplishment of his term being the purchase of Alaska from Russia.
I would place Rutherford B. Hayes right there alongside Johnson and Buchanan. He was a man who had lost in the popular vote to Samuel Tildon, but became president in a deal in the House of Representatives where the Republicans got their man in exchange for the end of Union occupation of the South. Because of that agreement, Hayes was a totally ineffective president.
