Hindsight & Afterthoughts
And yes, given that I'm an American of European descent and most of my readers live in either North America or Europe (Australia being a sort of Honorary European nation), this list ignores most of the contemporary multi-culti darlings. While The Tale of Genji may be an historically significant work, and I would personally like to make every Star Wars fanboy read The Tale of The Heike at light-saber point, I've completely ignored Chinese, Japanese, African, and Native American literature, for the simple reason that until recently, these have had next to no impact on the development of western civilzation. Again, we can discuss this, if you like.
I could go on and on, and sometimes do. Where's the Bronte, the Austen, the Scott? I wanted to put at least ten of Shakespeare's plays on the list; to pick one representative example was a tough call. Should Hemingway even be in such august company? Well, yes, for the same reason that I want to make people read at least two of Ferlinghetti's poems: one for the shock value, and another to prove that the first one wasn't a fluke, and both together to gently lead the reader to ask, "What the Hell happened to literature in the 20th century?" (The same thing as happened to art, I'm afraid.)
But if you're one of those people who wants to argue that I've committed a grave injustice here by not claiming that literature begins with the love poetry of Sappho and that the entire history of literature is one long tale of Eurocentric patriarchal oppression — well, there are websites for people like you. And this isn't one of them.