Lord of the Rings and other Tolkien works. Yes I know that they are beloved by millions, and are the grand-daddy if all fantasy, but they just haven't stood the test of time. Tolkien was a great world builder and linguist, but his storytelling is really bad when compared to today's writing. I'm of the opinion that these are books to read fully once, and then if you read them again, skip large sections to condense it all. They are worth reading to learn about the roots of fantasy, but those that read them all the time just need a life.
Tolkien's Farmer Giles of Ham (Wikipedia) is an exception. He actually pokes fun at the escapist sentimentality of fantasy novels like LotR: noble, valiant, self-sacrificing heroes etc.