You are talking about military leaders here, not pugilists. There is no way to know which would win in a fight, and it will never be possible to arrange such a fight either, since both are long gone.
Search it up.
it would probably be either George Washington or Abraham Lincoln
As someone writing from the UK, I would say George Washington or Abraham Lincoln.
Washington was between 6' 2" and 6' 4". Lincoln was 6' 4'' and was the tallest president, so far. Additionally, George Washington was powerfully built, and naturally athletic. Lincoln, was quite gangly, and was thought to suffer from Marfan's disease, which would cause him to have long, thin and weak limbs.
Follow your conscience, good luck and watch your back.
I would say George Washington, Abraham Lincoln, John F. Kennedy & Ronald Reagan.
As of 2009 George Washington would be 277 years old.
George Washington was a highly regarded general in the late 18th century. If I had a war to fight then, I would definitely hire him. However, he might be less effective in a war today, because the advances in weapons and tactics would be unfamiliar to him. After all, he died a century before the first airplane was invented.