With EA's Dante's Inferno game on the verge of release, draw your eyes to some lists of the 100 greatest books of all time. Few games have been made based on the books, for better or worse.
I found a Top 100 Books list from Newsweek (a meta list of other lists), posted last summer.
Books from this list that became games: #10 The Divine Comedy (Adapted as EA's Dante's Inferno), #35 The Lord of the Rings (Adapted via the book and movies.), #37 The Lion, The Witch and the Wardrobe (Adapted via a movie), #41 The Holy Bible (If you count Bible trivia games and (thanks, readers!) many other Bible-based games), #56 Mary Shelley's Frankenstein (Adapted via a movie for the Super Nintendo and Sega Genesis), #84 The Golden Compass by Philip Pullman (Adapted via a move, listed by Newsweek as part of the His Dark Materials series.)
I pulled a 2007 list from The Modern Library of the 100 best novels.
Books from this list that became games: None.
I also found this 2002 list from the Norwegian Book Club, which put Don Quixote at number one but otherwise stuck with alphabetical order.
Books from this list that became games: Fairy Tales and Stories by Hans Christian Andersen (If we're counting The Little Mermaid) and The Divine Comedy again.
Looking over these lists, I'm surprised there haven't been video games based on Gulliver's Travels, Lord of the Flies, Hear of Darkness, The Odyssey or anything from Shakespeare. Unless I missed them.
I'm sure gamers could nominate some books worthy of video game adaptations as well as warn off publishers from at least a few classics that just wouldn't work as video games.