FDR

He took the US from the bottom of the great depression to the number one superpower in the world. He created the most sweeping legislation for social justice with his New Deal. When most of the US wanted to "Let Europe deal with it's own problems," he had the foresight to get involved and end one of the greatest evils this world has known, the Nazi regime. He was such a phenomenally popular president, that he was elected to four terms.

By the way... he did this all while restricted to a wheelchair because he had polio.