In my opinion none of them were particularly good ...
Jimmy Carter is (easily) in the running for one of the worst presidents of all time, George W. Bush is a below average president in a presidency which was more challenging that most (and therefore he did a pretty poor job), and Obama is 2 years into a presidency that people either think he is a poor president because he did too much or a poor president because he hasn't done enough; and (therefore) none of these three presidents can really be considered.
Bill Clinton was a caretaker president. His greatest "accomplishment" was having projected budget surpluses which were based (at least in part) on the completely unsustainable dot com bubble; and the assumption that military could continue to shrink because there were no threats to the United States. When the dot-com bubble burst and 9/11 happened it should have been clear that his assumptions were wrong, and therefore his projections were wrong.
Which (effectively) leaves Ronald Reagan and George H.W. Bush ... I would personally favour George H.W. Bush because I think NAFTA is more meaningful to economic growth than Reaganomics, and that operation desert storm was a justified action.
