We've had 43 different people serve as president...?

So why do some hard wingers (both sides of the Isle) think that Bush (for Liberals) and Obama (for Conservatives) are the worst presidents ever? We've had even worse presidents like Carter (Good guy, bad leader, with the exception of foreign policy issues), Nixon (Corrupt), Hoover, Harding, Coolidge, Andrew Johnson, and James Buchanan. Why do they think that they always live in the worst of times?