Not Montgomery or McArthur. Monty was largely responsible for the Battle of the Bulge by allowing the Germans to escape in 1943. He made mistakes all over N. Africa too.
McArthur gambled the farm on Inchon and won. Had the weather been anything other than perfection, he would have been among the worst.
Patton never lost period. He showed the world how to use armor and air power with almost precision coordination.
Washington did a whole lot with a very little. I'd have to say he's got to be up there.
In one of history most daring military moves ever. I think a little credit is deserved here. It is the mark of a great commander to pull victory from certain defeat, that is what defines a great commander.