10. Ulysses Grant & Robert E. Lee
Another historical rivalry, albeit less personal than the preceding one, Grant and Lee were the respective commanding generals for the North and South armies during the closing years of the American Civil War. Grant was the last in a long line of Northern generals who had been unable to take advantage of their superior numbers against the south. After he was handed control, Grant waged a relentless offensive that ignored all setbacks and eventually wore down the Southern armies to the point of exhaustion and malnourishment. Lee had been leader of the Virginian army for most of the war, despite his private reservations about the South's chances, and he had been enormously successful against the North's larger and better equipped armies before eventually being forced to surrender due to his troops exhaustion and lack of provisions. The film could follow their lives starting with them fighting alongside each other in the Mexican American War leading to the cat and mouse game between their respective forces at the end of the Civil War.
Casting Choice: Viggo Mortensen would be an interesting choice for Grant. Lee has already been portrayed by Robert Duvall and Martin Sheen so I think another veteran character actor would work best.