Not that it needs any marketing, being the novel it is, but The Great Gatsby is kind of a brilliant name. Imagine if it were named “The Forlorn Gatsby” or “The Unfortunate Tale of Jay Gatsby”. Doesn’t work.
The Great Gatsby has a strong adjective that gives it weight, alliteration that gives it flow, and the genius limitation of only two words. Additionally one who has read the book can recognize the solemn irony that petrifies the title into the classic it has become.