I do believe that Abraham Lincoln was the greatest American President. Washington did have a difficult task as the first American President, but Lincoln had to truly define what our nation really was in order to make decisions during the Civil War. Our country went into that war as a Union of virtually independent states and came out of it transformed to Lincoln's view of a indivisable nation. At the beginning of the Civil War a man like Robert E. Lee could claim that his loyalty to his state was more important to his loyalty to his country - at the end of the war, the country became more important than the state. It was Lincoln who really conceived the difference and reformed the nation in that image.
This is a great question!
I find George Washington, not Abraham Lincoln, to be our greatest president. I would rank Abraham Lincoln a close second, though. I find George Washington to be our best president because he fought for SO many years as our general (and did a great job overall) and then was able to get the members of the constitutional committee to come together, although there were many disagreements and at times, hard feelings. Finally, he had the daunting task of being the very first president of a brand new country and no one else could have been in that position except Washington. He was the only leader who could tackle that position.