I’d rank them 20th century:
Coolidge, Reagan, Bush II, Eisenhower (recall he built the interstates), Taft and then Harding. Harding wasn’t around for very long, which makes it difficult to rank him up there with Taft who was full term with similar policies.
Taft royally pissed TR by jettisoning the progressive agenda and sticking with conservative principles. Which gave us Wilson after TR ran with the Bull Moose.
On the Dim side:
FDR, Wilson, Obama, Carter. Carter really deserves to be higher then Truman, Truman cut the post WW2 deficit and his administration paid off substantial amounts of debt. Makes him a giant compared to Carter.
As for the 19th century. Obama is a dead ringer for Franklin Pierce, one of the very few single termers on either side who failed to acheive his own party’s nomination after completing a full term. Which makes Pierce and Buchanan right up with Obama and Carter as the worst single termers. Wilson got re-elected which gave him significant time to do damage to the United States.
I tend to cut both Buchanan and Pierce some slack, but for different reasons. Pierce was largely inebriated and bitterly unhappy for the bulk of his term, and shortly after his election, his last living child was crushed to death in a train as he and Mrs. Pierce watched in horror. He was ill-prepared to deal with the dicey situation nationally, and had no moral support from his wife, who was a profoundly depressed basketcase and had begged her husband to stay out of politics entirely (for which probably would’ve spared their son and not plunged the Pierces into such misery).
As for Buchanan, I also considered him to be in a terribly uneviable position as President. As a 1850s Democrat, he had to walk a fine line between appeasing anti-slave Northerners and pro-slave Southerners. Any decision he made would enflame either group and if he took decisive action early on, it just would’ve brought on war that much earlier. It didn’t help matters that his VP and many members of the cabinet were viscerally pro-Southern. Once the 1860 election occurred, it gave him the only opportunity to step up as he saw the pro-Southern Cabinet faction aiding their cause (which by all accounts would be considered treasonable) and he forced out or urged the resignations of all but the Navy Secretary. Lincoln would end up retaining Buchanan’s replacement as Attorney-General, Edwin Stanton, shifting him to the War Department.
I’m not sure what the net difference would’ve been had Pierce been defeated by Whig Winfield Scott. As was pointed out elsewhere, Scott differed little in his campaign platform from Pierce (aside from being anti-slave). The Whigs were already collapsing in 1852 (and would run their final candidates in the ‘54 midterms), and like with the Democrats, they also had a tenuous coalition of Northern abolitionists and Southern (pro-slavery) Aristocracy, and it was just as easy to piss off either group with any stance.
As for 1856, with the first candidate of the Republicans, it would’ve been interesting to see how John Frémont would’ve presided. However, as with Lincoln, it ultimately would’ve caused secession four years ahead of schedule, and Frémont would’ve been the “War” President. At least Pierce and Buchanan could claim their elections didn’t immediately precipitate war, something Lincoln (or Frémont) could’ve claimed. Perhaps better than nothing.
True, that's an accomplishment at least, even though he was a big government RINO type. That puts him ahead of the likes of Poppy Bush and Ford. I give Poppy a point for Clarence Thomas, that's about it.
I'm very low on W. Bush especially his big government second term. Maybe the passage of time will alter my perception. He is by default the best President of 21st Century, which ain't saying much. ;)