|Trust me on this...I know how to read.|
Look at it this way: The Great Gatsby could pretty much take place anytime, anywhere. It's basically a timeless treasure. The Sun Also Rises, on the other hand, is a novel strictly of its time and place. One can find Gatsby-size parties throughout the globe, for instance. Bullfighting, however, is pretty much restricted to parts of the Spanish speaking world.
What's more, Hemingway's masterpiece focuses on themes relative to the geographic and historic location of its narrative. While disillusionment, aimlessness, and the cloud of war may indeed haunt millions, the theme of Fitzgerald's opus - that of a longing for the past - is universal.
So why the mixup? Why is The Great Gatsby, rather than The Sun Also Rises, widely acclaimed as the jazz-age novel? For one thing, more people read Fitzgerald's classic than Hemingway's. The Great Gatsby is a high school staple. I can't say the same for The Sun Also Rises, although it clearly remains a hugely popular work.
Another problem is Fitzgerald himself. A full fledged celebrity during his youth, the author; along with his wife, Zelda, were the hot couple of the 1920s. By the time the 1930s rolled around, however, the duo was slipping from the spotlight. Fitzgerald was being marginalized by his alcoholism while Zelda was being marginalized by Schizophrenia.
Hemingway, on the other hand, was a celebrity most of his life. Not only was he well known in the 1920s, he was enormously famous until his death in the early 1960s. Most people see Hemingway as an aging man with a gray beard. Fitzgerald, however, appears in the public consciousness as a young, jazz-age success story.
Of course, none of this really matters in the end. Both The Great Gatsby and The Sun Also Rises are literary caviar and well deserving of their fame. If you're going to ornament a novel with a description, however, make sure that description is accurate.