The friendship between Nick and Gatsby is rather an intriguing one. The two men do appear to have a genuine regard for each other, but there are hints of ambivalence in their relationship. It could be argued, for instance, that Gatsby essentially uses Nick to get closer to Daisy, Nick being Daisy's cousin, while the friendship on Nick's side is qualified by the fact that he is forever analysing and judging Gatsby. Yet, we cannot overlook the fact that Nick does appear to really admire Gatsby and certainly prefers him to the rest of the shallow, self-serving milieu in which he moves. (In spite of his claim to honesty, Nick can, indeed, be accounted something of a hypocrite, as he continues to move in social circles that he professes to despise.) Gatsby, too, appears quite affectionate towards Nick. There is a telling moment during their very first meeting, at one of Gatsby's parties, when Gatsby greets Nick with a warm smile full of understanding: 'one of those rare smiles with a quality of eternal reassurance that you may come across four or five times in life' (chapter 3). Gatsby appears to be one of a kind for Nick in the genuine sense of warmth that he projects.
Nick is certainly struck by Gatsby, and likes him, while never relinquishing his role throughout the novel as his most critical observer. As everything in the novel, including Gatsby, is filtered through the consciousness of Nick as narrator, we can never be exactly sure what Gatsby is thinking, what his ideas and motives really are, and this poses a bit of a problem when trying to assess the friendship between him and Nick. However, we can say with some confidence what attracts Nick to Gatsby; he sees right through the more superficial social side of him, straight through to his dreams and ideals. For Nick at least, Gatsby pursues a worthy goal in trying to reclaim the happiness and love of his past with Daisy, even if he goes about things the wrong way by stacking up his wealth and social status in order to try and impress her. But the very fact of him having a dream, an ideal, to pursue, is what makes him admirable in Nick's eyes and quite different from most other people who are simply greedy, selfish, and materialistic.
In short, Nick, himself a sober realist for the most part, is attracted to Gatsby's sense of romantic idealism which elevates life:
there was something gorgeous about him, some heightened sensitivity to the promise of life ..... 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. (chapter I)