Charlemagne. He was not only a divider (of the enemy's head from his shoulders), but a uniter as well.
The Duke of Wellington (took out Napoleon)
Sun Tzu (maybe not strictly a commander, but he talked a great game)
Patton (50,000 more gallons of diesel and he would have been in Berlin playing mumbledy-peg with Hitler).
And speaking of Napoleon, that little Corsican pipsqueak is definitely NOT on this list.
Not sure I agree with your assessment of "The Duke"...Napoleon was the runt fighting in a room full of big boys and winning....Napoleon just went "A Bridge Too Far"...I'm not sure if he could have kept his conquest and reshaped Europe...but when everyone on the block is after your ass...he should have went defensive instead of offensive and worked the people into a fury over their previous rulers...if he had done that...for sure no WWI or WWII....not sure how exactly Europe would have turned out but for sure no World War I and II......