[quote name='elprincipe']1. George Washington - if only we had listened to him and avoided forming political parties, the cancer of our political body.
2. Thomas Jefferson[/QUOTE]
Wait, the reason you give for your #1 pick is his advice against forming political parties, and for #2 you list the main person responsible for the formation of political parties in the US? Not that I'm really disagreeing with your pick, but that just stood out to me
Anyway...
1) Washington - I think its very hard to debate this one. Washington set SO many of the protocols and traditions for what the president should be that stand up to this day. Even the simple address of 'Mr. President' is what he chose, over many titles that others wanted that he felt were too deferential. He helped design Washington D.C., including the White House. Probably his greatest legacy is in choosing to step down after 2 terms and peacefully handing over the office to another (despite the fact that there were MANY who wanted to make him King George.) The United States owes a LOT to Washington.
2) Lincoln - not much needs to be said. Held the country together when it otherwise would have split.
3) FDR - Created so much of what we think of as 'modern America', which has withstood despite decades of Republicans trying desperately to tear it down.
4) Jefferson - It gets harder at this point. I guess I would have to go with Jefferson. (Most of his greatest accomplishments happened before he was elected to office, which is the reason for my hesitancy. He definitely was a great man, easily on-par with Washington. His term as president, though, wasn't quite as great.) His policies of expansion (including the Louisiana Purchase) did a lot to form the US as it exists today.
5) Theodore Roosevelt - even a harder pick, but I would give it to Theodore. He played a major role in the creation of what would eventually become the FDA. He also did a lot of fighting for workers rights and limits on corporate power (though he mostly lost on those issues, during his term in office, though his support eventually did reap rewards by bringing it to the public conciousness.)