My picks, I suppose, would be as follows: I think that Reagan, Kennedy, and Clinton are probably the three most overrated 20th century presidents, and Eisenhower, Carter and Ford are the most underrated. This does go against my partisan leanings a bit, but that's what I think. Reagan is such an obvious case that it almost needn't be argued--virtually everything that he's beloved for he didn't do, and virtually everything he actually did has been forgotten. Yes, he cut taxes, but then he raised them a half-dozen times to balance the budget, and then he just decided not to bother balancing the budget, thus virtually ending the (good) conservative tradition of balanced budgets. Yes, he beat the Soviet Union, but not by the force of personality or standing tall or whatever he was supposed to have done with Khadaffy, but largely by adept diplomacy. Reagan was effective, no doubt, but the messiah mythos that has developed around the man is not really earned. Kennedy isn't a hard case either: he was no liberal, indifferent to organized labor, extremely hawkish, and whose commitment to things like ending poverty (unlike his brother's) seemed little more than a political calculation. And Clinton's presidency, though well-run in most respects, was a parade of missed opportunities and personal failures.
As for the underrated ones, Ike was simply too good, and far craftier than people realized. Great on foreign affairs, and good on most domestic issues as well. Perhaps his greatest failing was putting Dick Nixon on the ticket, thus subjecting this nation to that man for decades, but nobody's perfect. Carter is generally believed to be a bad president, which is not entirely untrue, but things only really started to spiral downward during his last year in office. He was every bit as effective a peacemaker as Nixon, and were it not for the perfect storm of stagflation, the hostage crisis, and the conservative tailwinds in the country at the time he might well have won in 1980. Maybe. He wasn't great but he wasn't a bottom-five president either. And Jerry Ford wasn't too bad a president, all things considered.
The worst president of all time, though, had to be Grant. He was a pretty bad general, too. Sure, he was better than McClellan if for no other reason than that he would fight the rebels, but his tactics were no more sophisticated than just throw my guys at your guys, on the theory that I can sustain more losses than you. One wonders whether the Army of the Potomac wouldn't have been better off under Meade--who beat Lee at Gettysburg, something that Grant never really managed to do--or maybe Hancock. The Union army had worse leadership, to be sure, but someone with more imagination and talent than Grant might have ended the war sooner, I think. And as for his presidency, it's best left to H. L. Mencken, who sums it up nicely:
"His belief in rogues was cogenital, touching and unlimited. He filled Washington with them, and defended them against honest men, even in the face of plain proofs of their villainy."Well put, characteristically.