Based purely on how much they changed the government to ignore the Constitution ... I would say Lincoln and FDR were the worst Presidents we've had. They both set the stage for Obama's ignoring it (with the "Affordable Care Act").
Just because times are bad does not mean the president is a superhero who would have the power to shower us with money and peace. He's doing the best he can and, if you ask me, maaaaany other people would have dug America's grave deeper. He may not be keeping us totally above the ground, but he||, consistency is better than an all-out crash. Being the president at a time like this ain't a picnic. Poor guy inherited a lot of issues, but he is certainly doing his best. Red out.