From Wikipedia comes this definition. Does it sound like anyone we know? One name jumps right out at me ...

Megalomania (from the Greek word μεγαλ&... is a historical term for behavior characterized by delusional fantasies of wealth, power, genius, or omnipotence - often generally termed as delusions of grandeur or grandiose delusions. It's a Greek word ,"megalo" meaning "very large", "great", or "exaggerated" and "mania" meaning obsession thus combining to denote an obsession with, either in the form of irrational perceived need for or preoccupation with in one's own estimation having and/or obtaining, grandiosity and extravagance (especially in the form of great fame and popularity, material wealth, social influence or political power, or more than one or even all of the aforesaid) and accompanying complete desirous and bombastic abandon; a common symptom if not the key diagnostic feature of megalomania. It may be a symptom of manic or paranoid disorders