Robert Lee's decision represented the defining moment of America at that time. It was a deeply felt decision from conviction, not the superficial kind of pettiness we see so much of today. He is a man one can totally disagree with and totally respect at the same time.
None of the generals in the war of 1861 - 1865 was very great, certainly not in the sense of Napoleon as a tactician. The major error of all of them is that they were still fighting their idea of an army from his period.
If Napoleon had been the Northern Army commander, the war would have been over by late 1862 at the latest.
Lee did pull off some impressive things in the context, though. Crossing the Peninsula with his flank to McClellan was audacious if not fool-hearty.
Was it Bedford Forrest who was the remarkable southern commander? If I'm thinking of the right guy, he was impressive, especially considering he really came from a non-military background. Maybe that substantiates what I said about fighting-the-last-war thinking. He knew his terrain, his men and his weapons without too much learning of what can't be done.
Both sides fought for their concept of freedom; that's the saddest thing about that unnecessary war.