As far as intelligence goes, it manifests itself by the choices people make. Vito died saying that life was so beautiful; Michael died alone with a little dog his only company, a consequence of his choices.

Also, I'm not buying the no choice. "Leaving" his father might have seemed analagous to patricide, but it was still a choice. I would have murdered to protect my father, but now that he is dead, there is nothing to protect that would warrant murder. It's all perception. Michael perceived that murder was to be used quite frequently for him to get his way. To tell you the truth though, I don't think he knew what "his way" was. His father did. Now, that's intelligence.