Several readers have found expressions of Nick’s attraction to Gatsby in the narration. Edward Wasiolek pointed out that Nick’s portrait of Jay Gatsby, a criminal and adulterer, is unjustifiably positive on the face of it, so that we need to deduce a hidden motive:
There is the possibility that Nick’s defense of Gatsby and his eagerness to think the best of him and the worst of Tom, hide reasons other than those general, impersonal, and honorific reasons that Nick gives.
Edward Wasiolek (1992). ‘The Sexual Drama of Nick and Gatsby’. In The International Fiction Review 19.1, p. 15.
Traditionally Nick’s admiration of Gatsby was explained with reference to his “incorruptible dream”, but Wasiolek directs us to phrases in Nick’s first description of Gatsby that suggest a romantic attraction:
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, some heightened sensitivity to the promises of life, as if he were related to one of those intricate machines that register earthquakes ten thousand miles away. This responsiveness had nothing to do with that flabby impressionability which is dignified under the name of the “creative temperament”—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.
F. Scott Fitzgerald (1925). The Great Gatsby, chapter 1. Project Gutenberg.
To these we can add Nick’s description of Gatsby’s smile:
He smiled understandingly—much more than understandingly. It was one of those rare smiles with a quality of eternal reassurance in it, that you may come across four or five times in life. It faced—or seemed to face—the whole eternal world for an instant, and then concentrated on you with an irresistible prejudice in your favour.
Fitzgerald, chapter 3.
And Nick’s decision to skip work to go swimming with Gatsby:
It was nine o’clock when we finished breakfast and went out on the porch. The night had made a sharp difference in the weather and there was an autumn flavour in the air. The gardener, the last one of Gatsby’s former servants, came to the foot of the steps.
“I’m going to drain the pool today, Mr. Gatsby. Leaves’ll start falling pretty soon, and then there’s always trouble with the pipes.”
“Don’t do it today,” Gatsby answered. He turned to me apologetically. “You know, old sport, I’ve never used that pool all summer?”
I looked at my watch and stood up.
“Twelve minutes to my train.”
I didn’t want to go to the city. I wasn’t worth a decent stroke of work, but it was more than that—I didn’t want to leave Gatsby. I missed that train, and then another, before I could get myself away.
Fitzgerald, chapter 8.
None of these indications are explicit or unambiguous, so other interpretations are consistent with the text: that Nick admires Gatsby, or envies his success, or believes in his “incorruptible dream”, or all of these.