Nick opens the story by telling the reader that he is inclined to "reserve all judgments." He establishes himself as a reliable narrator. More importantly, regarding his character, he proves himself to be an honest man. At the end of Chapter 3, he says, "Every one suspects himself of at least one of the cardinal virtues, and this is mine: I am one of the few honest people that I have ever known." Nick is honest. This is why he disapproves of the society he encounters in the novel. There is a lot of lying, cheating, and elitism in the social circles that Gatsby, Daisy, Tom, and Jordan Baker move in.
Nick correctly perceives Tom as a brute, a racist, and an elitist. Tom cheats on Daisy with Myrtle. Myrtle believes that Tom will eventually leave Daisy for her. Myrtle acts with the snobbery that she thinks naturally comes with living in Tom's world. Nick sees this snobbery in Myrtle's friends and describes her with disdain in Chapter 2, "She looked at me and laughed pointlessly. Then she flounced over to the dog, kissed it with ecstasy and swept into the kitchen, implying that a dozen chefs awaited her orders there." Nick is also appalled when Tom violently breaks Myrtle's nose. Early into his stay in the New York area, Nick has encountered lying, cheating, and violence.
But Nick does enjoy the excitement of living in New York. Near the end of Chapter 3, he says, "I began to like New York, the racy, adventurous feel of it at night and the satisfaction that the constant flicker of men and women and machines gives to the restless eye."
But by the end of the novel, he will have developed a distaste for the lying, cheating, and elitism he will experience. And although Gatsby has an affair with a married woman and has shady business dealings, Nick comes to admire him. Nick recognizes the youthful idealism and romanticism of Gatsby. To Nick, he is therefore more genuine than anyone else. In Chapter 8, after Tom and Daisy have planned for their trip to abroad, following the car accident, Nick says to Gatsby, "They’re a rotten crowd,’ I shouted across the lawn. ‘You’re worth the whole damn bunch put together."
In Chapter 9, when none of Gatsby's so-called friends show up for his funeral, Nick is appalled. He does manage to summon and meet Gatsby's father. But Nick realizes even more fully that Gatsby's party crowd simply used him and his house as an elite social gathering place. He can't even get Wolfshiem to come to the funeral.
Near the end of Chapter 9, Nick praises his memory of the Midwest. This idyllic culture is in contrast to the chaotic, deceitful culture he has experienced in New York (the East). He says:
Even when the East excited me most, even when I was most keenly aware of its superiority to the bored, sprawling, swollen towns beyond the Ohio, with their interminable inquisitions which spared only the children and the very old—even then it had always for me a quality of distortion.
Nick appreciates the excitement of New York City but also longs for the honest simplicity of the Midwest. This is complicated by the fact that he, Gatsby, Tom, Daisy, and Jordan were all once from the Midwest. He concludes that perhaps there is something common to all of them that makes them unable to adapt to Eastern life. So, Nick was enamored with how exciting city life could be, but he developed a strong distaste for the corruption and lying that tended to dominate the social world that he experienced.