Washington, Lincoln, Jefferson, FDR on my short list.
I have Washington out front. Many posts in this thread talk about him being overrated but I believe he is in fact underrated.
There are Presidents who have accomplished more during their Presidency, but Washington's impact on the office itself cannot be overstated. I really believe that ANY other man from Jefferson, to Madison, etc. and the U.S. would not have been as successful in those early years, and may have in fact collapsed a bit. (I don't think completely because along with Washington you had a large collection of extremely capable politicians, which is something the British didn't take into account... and I'm getting off track).
Washington is still the standard bearer for the office. Here, I advise you to read his farewell address
All of the founding fathers, indeed even the Revolution itself, if muddled with myth these days, but Washington is the one man that, the farther I go into history, he still seems to live up to it.