Perhaps we've lost the thread. We measure or assess Michael against the background of his family. We don't know the backgrounds of Barzini, etc. We compare Mike with his father and brothers because that is pretty much all we have to work with.

I think we are debating degress of pathology. As I have stated in a previous post, Michael was a sometime imitation of his father - intelligent, but not as intelligent as his father. The ability to kill as Vito and Michael did is a functionof some degree of alacrity - in their cases, a measure of the value of life. They are all sociopaths (witht he possible exceptionof Fredo) to a degree. Michael was in the best position to leave it all behind. He chose otherwise.