The Great Gatsbt Remix

Why is Nick so obsessed with Gatsby? He states that at the beginning of the story, but never really explained why? What makes him so likeable? In the beginning he mentioned that he did not like Gatsby but his opinion was changed. We didn't really find out much about the so called "Great Gatsby". Only at the end of chapter one where he finally marks his debut, but they were only subtle hints on what he can possibly be. We pretty much know nothing of him. I just wonder, what kind of a man can Gatsby be for somebody like Nick be so obsessed with?