In no order...
Clinton - I really don't care what he did sexually or with who, it doesn't change the fact that the man was/is a dipolmatic genius. He a charisma, a way with words, an intelligence, that elevated him. He was THIS close to having a peace deal with Isreal/Palestine. Only reason it didn't happen was because Arafat didn't accept it in time. By the time he did, GWB was in office and the deal wasn't on the table anymore(boo).
Carter - I know he wasn't a very effective president, and yes, we can thank him for credit card inflation. But he is a good man. An honest man. And he had nothing but good intentions. I'd like to see that more often in politicians. He had a down-to-earth-ness, an inherent decency and honesty, that men like John Kerry and GWB could never dream of having.
FDR - Got us through WWII and the Depression. Put the New Deal in place. Got elected to FOUR terms, and is the reason we limit presidents to two terms now.
Kennedy - Was very idealistic, strived for unity. In terms of ideals and goals and desires, reminds me of MLK more than any other president.
Lincoln - the only Republican to make my list. Got us through the Civil War. Ended slavery with the Emancipation Proclamation. And when you make a speech like the Gettysburg address..."a house divided against itself cannot stand"...you become one of the great presidents. Those words could fit the current political landscape in this country like a glove.