The key to Gatsby's romanticizing Daisy is his admission to Nick, Daisy, and Tom:
He wanted nothing less of Daisy than that she should go to Tom and say: "I never loved you.." After she had obliterated four years with that sentence they could decide upon the more practical measures to be taken. One of them was that, after she was free, they were to go back to Louisville and be married from her house - just as if it were five years ago.
"You can't repeat the past.."
"Can't repeat the past?." he cried incredulously. "Why of course you can!."
"I'm going to fix everything just the way it was before,." he said, nodding determinedly.
Also, look at Fitzgerald's use of water imagery: rain and tears to show over-emotion, sentimentality, and romanticized love. Specifically, look at the scene where Daisy cries over Gatsby's shirts. Gatsby wants it all: both love and money; Daisy just wants money. She begins crying when she realizes that she can't repeat the past, that she doesn't love anyone any more. She knows she already has money and can't leave Tom for the romantic Gatsby:
He took out a pile of shirts and began throwing them, one by one, before us, shirts of sheer linen and thick silk and fine flannel, which lost their folds as they fell and covered the table in many-colored disarray. While we admired he brought more and the soft rich heap mounted higher - shirts with stripes and scrolls and plaids in coral and apple-green and lavender and faint orange, and monograms of Indian blue.
Suddenly, with a strained sound, Daisy bent her head into the shirts and began to cry stormily.
"They're such beautiful shirts,." she sobbed, her voice muffled in the thick folds.
"It makes me sad because I've never seen such - such beautiful shirts before.." After the house, we were to see the grounds and the swimming-pool, and the hydroplane and the mid-summer flowers - but outside Gatsby's window it began to rain again, so we stood in a row looking at the corrugated surface of the Sound.
Your question concerning The Great Gatsby suggests one way of looking at the issue you raise. Gatsby certainly views Daisy and his relationship with Daisy in a romantic and idealistic manner. He believes Daisy is the perfect woman for him and that Daisy loves him and has been pining for him all these years. He believes Daisy never really loved Tom and just married him for his money.
His illusion is destroyed when Daisy refuses to say that she never loved Tom. Gatsby wants her to say it and come away with him, but she refuses to say it and does not leave Tom for him. These actions destroy Gatsby's illusion.
Still holding on to some hope, Gatsby waits for a phone call from Daisy the next day, but the phone call never comes.
Thus, the novel is filled with Gatsby's love for Daisy, but in the end Daisy's love for Gatsby falls far short of his expectations. When he discovers this, his illusions are proved to be false.