I don't approve of Napoleon myself. But when an expert in any field is speaking on his area of expertise, I listen very carefully. I've known people who were grade-A jerks on a scale almost beyond belief, but were very good in one particular area, and when they spoke about the areas that they were good in, I perked up and paid attention.

And as far as unwarrantedly calling someone "The Great" goes---I'd put Justinian I of Byzantium in that category. His wars devastated Italy and left it open to the Lombards, who were quite a bit more barbaric than the Ostrogoths he'd destroyed; his policies did a lot to weaken his Empire in the long run, and his conquests outside Italy were evanescent at best.