Note: Although I strongly disagree with him on most things, Obama gets a pass since he's only been in less than 100 days. In fact, it will be similarly difficult to judge President Bush--the lens of time changes opinion on Presidents. But since there are such strong feelings about the man on both sides, I figured it only fair to include him.
Since I was limited to 5 options, I exercised my own opinion somewhat and left off Ford, Reagan, and Bush 41. Those Presidents are generally regarded ranging from benign to great, so there were better (worse?) choices to pick from out there.