FDR was a socialist and should be disqualified on that basis. He put everyone back to work, but changed the tax structure in such a bad way, that we still feel the effects today. His great plan of social security drags the economy down today. 3% of my money goes into a fund that will never benefit me. I feel like I could donate that money to charity and have it do some good instead of having it tied up in a massive bureaucracy. And bureaucracy was never a problem before FDR, now we pay so much in taxes because we have to pay millions of federal workers, most of which do the same job as ten other people and aren't needed, because of FDR. He won World War II, but documents released because of the freedom of information acts show him telling his admirals to not inform Pearl harbor that a Japanese attack was coming. So his insistence that we get into that war led to thousands of deaths.
I would go with Lincoln, except there was only one issue during his Presidency, and I don't think slavery was the top reason for the Civil War. The north was crushing the south economically, and like always the fucking yank bastards felt that it was their job to tell the south what to do. Not help with technology that they had, just telling the south that the way they had done things for 200 years was now going to be outlawed. The north wanted to crush the south because of a northern inferiority problem that they still have today. Slavery was a good propaganda reason for the north to fight the south, but northern imperialism is the real reason for that war. Lincoln himself stated that he didn't care if there were slaves or not, he just wanted to hold the country together.
I am going to pick Ronald Reagan. Before Bill Clinton sent all of our jobs overseas, Reagan's teory of trickle down economics made this country financially strong. Manufacturing jobs were available everywhere, for a good wage because the tax breaks he gave on capital gains were used to pay employees well down the chain. It ook him 20 minutes to free the hostages that Jimmy Carter couldn't free for two years. He built up this nations military citing theories that no one attacks that which it can't beat. Peace through strength. Reagan ended the Cold War and communism without ever firing a shot. He had more bipartisan cooperation in congress than anyone after him. People got rich, Wall Street got huge, and people started to own things. Stock went froma rich man's game to a viable savings option for everyone. People retired more comfortably and started careers with better pay.
There is no big shining moment during Reagan's Presidency, but his policies are what led to the economic growth in the 90's and to the protections consumers feel today on faulty products. He made this a richer safer world, and a richer safer country.