Clinton and Obama are similar in how good of Presidents they are, both very flawed with some good policies.
Reagan and W compete for the bottom spot, Reagan ahead on long-term bad direction, W ahead on utter selling out.
Carter was a lot better than people think on policy. He passed more of his legislative program than any Presiden since. He fell short on leading.
If Carter had the right-wing publicity machine behind him, we'd all hear how he defeated the USSR by drawing the Soviets into Afghanistan, fixed he broken economy by appointing Paul Volcker, kept us out of war, was the last President with fiscal responsibility before Reagan blew up the debt, was ahead of his time on our energy policy, of course the Camp David peace accords, and more.