Very early in the opening chapter of F. Scott Fitzgerald’s novel The Great Gatsby, Nick Carraway, the narrator of the book, indicates fairly explicitly the impact the other characters have had on him. The story is told in retrospect, and so Nick is able to look back at the other people in the narrative and say this:
When I came back from the East last autumn I felt that I wanted the world to be in uniform and at a sort of moral attention forever; I wanted no more riotous excursions with privileged glimpses into the human heart. Only Gatsby, the man who gives his name to this book, was exempt from my reaction--Gatsby who represented everything for which I have an unaffected scorn. If personality is an unbroken series of successful gestures, then there was something gorgeous about him . . . -- it was an extraordinary gift for hope, a romantic readiness such as I have never found in any other person and which it is not likely I shall ever find again. No--Gatsby turned out all right at the end; it is what preyed on Gatsby, what foul dust floated in the wake of his dreams that temporarily closed out my interest in the abortive sorrows and short-winded elations of men.
In other words, although the book will reveal various flaws and foibles in Gatsby himself, Gatsby ultimately strikes Nick as an admirable character. The same cannot be said, however, of Daisy and Tom Buchanan. Indeed, near the very end of the novel, Nick – in a passage that exists in a kind of symmetrical relationship with the one just quoted – comments that
They were careless people, Tom and Daisy--they smashed up things and creatures and then retreated back into their money or their vast carelessness or whatever it was that kept them together, and let other people clean up the mess they had made. . . .
To add to the structural symmetry, Gatsby is explicitly praised as the book comes to its conclusion. Thus the novel ends as it began: with a generous assessment of Gatsby and with open condemnation of the two most important people with whom he became involved.
Thus the effect of most of the other characters on Nick is double-edged: Gatsby mainly impresses him and gives him some reason for hope; the others mostly disillusion him and thereby make him appreciate all the more the rare and admirable qualities of Gatsby’s character.
Something extra:Fitzgerald's novel invites attention from many different critical perspectives, and indeed one of the most helpful books ever published about this novel is titled Critical Theory Today: A User-Friendly Guide, by Lois Tyson. Tyson offers readings of the novel from a wide range of critical perspectives, including psychoanalytic, Marxist, feminist, formalist, reader-response, structuralist, deconstructive, new historicist, queer, postcolonial, and African-American points of view. Ultimately, Tyson's book is an exercise in "pluralist" criticism, which assumes that each critical perspective is like a different kind of tool, useful in doing the particular job for which that tool was designed. Just as a hammer is no "better" than a screwdriver (since each is designed to do a different kind of job), so one kind of criticism is not necessarily "better" than any other kind. Just as one chooses the tool appropriate to a given task, so one chooses the critical method appropriate to the kind of reading one wishes to undertake.