Nick is honest and he prides himself on this attribute. He comes from the Midwest and honors the simplicity and honesty that is (sometimes stereotypically) characteristic of small town America.
The book begins with Nick’s description of his father’s advice about honesty and objectivity. His father warned him about criticizing others who have not had the advantages he has enjoyed. These advantages are not jus monetary. He is referring to being born into a family and society that stressed honesty. Consequently, Nick says that “I’m inclined to reserve all judgments” (1). From the very beginning of the book, the narrator declares that he is as honest and objective as he can be. There are limits to his objectivity, but the first few paragraphs of the novel definitely establish Nick as an honest guy and a reliable narrator.
Within the context of the novel, Nick stands out because he is surrounded by dishonest people. So, Nick thinks he’s one of the few honest people, because beyond the world of small towns, he has found few honest people.