I have a hard time choosing between Fitzgerald and Hemingway. They're both amazing but have completely different styles and write about different things. I like the fact that they wrote at the same time and were friends. If I had to pick between the two I'd say, Fitzgerald.
My three favorite books by Fitzgerald are; This Side of Paradise (my favorite), The Beautiful and Damned, and The Great Gatsby.
My three favorite books from Hemingway are; The Old Man and the Sea, The Sun Also Rises, and For Whom the Bell Tolls.
They both also have amazing short stories.