I just checked the Modern Library's 100 Best Novels of the 20th Century. It was limited to 400 novels published by Random House.
The top five are
1. Ulysses
2. The Great Gatsby
3. A Portrait of the Artist as a Young Man
4. Lolita
5. Brave New World
They seem to love Joyce as they also have Finnegans Wake as #77!
Modern Library Top 100 - Penguin Random House