The greatest President is George Washington. Everybody else is playing for second. If he hadn't been such a great president there wouldn't even have been any other presidents to compare with him... He would have been King.
It is waaay to early to rate Clinton, Bush or Obama. People get lost in politics i.e. their political views and don't see things clearly. IMO Bush/Obama will have a clear winner some day and it will be based on the Middle East. Bush... American military to secure stabilization of the middle east, Obama... gambling that democracy/Arab Spring and moving away from Pro-Israeli stance will create peace and stabilize region. If he is correct he will look like a genius. If he is wrong don't be surprised if there is another World War.