Some modern psychologists may call this a personality disorder. In ancient Rome, most people, especially among the power elite, would have called this normal cultural values.
Caesar's quest for glory, fame, power and legacy, and his faith in his own abilities (and his own perception of his family's supernatural origins and destiny) differed from the average Roman patrician only to the extent to which is was plied. Caesar's boasting of his descent from Venus was considered excessive by his peers, but he was not considered inherently dangerous or crazy because of it - such things are ultimately sanctioned by a pre-Christian worldview.
To judge the historical and cultural context in which Caesar's personality operated, I think we have to throw out some of the "moral" presumptions of the modern world forged by mainstream religions, philosophies and psychological analysis.