Reading Fitzgerald’s “The Great Gatsby” is hardly daunting, its an easy read. Anyone of Joyce’s tomes should be at the top of the list because you’d have to be a masochist to want to wade through them, even though they are of significant literary importance.
Dubliners and Portrait of the Artist were very good for their style and the emotion they evoked. Ulysses is like trying to climb a very tall mountain. After a while you feel "there's some fantastic views, but God, is it tiring." "Finnegans Wake" is like trying to climb Everest - without supplemental oxygen.