1. A Song of Ice and Fire, by George R. R. Martin
I picked up A Game of Thrones because my then-fiance bought a copy. He loved the book and encouraged me to read it. I found it so gripping that I stayed up all night reading it, unable to put it down. It's epic and emotionally intense, and the world Martin creates is rich and fascinating. Still, what I love most is the deep complexity of the characters. Too many writers create one-note villains, people just born evil with no valid point-of-view. While some of Martin's secondary characters, like Gregor Clegane, are pure savages, his main villains have a depth of character and a point of view that is almost as compelling as the heroes'. A reader might hate Cersei Lannister, and with good reason--but Martin shows that she fights to protect her children and save her loved ones. Even Ned Stark feels some sympathy for her; he knows that Robert treats her horribly, and that Robert would murder her and her children if he discovers her secrets. Excellent fantasy books need more than a fascinating world; they also need complex characters with gripping stories readers can't put down.
2. His Dark Materials, by Phillip PullmanIn his books, Pullman creates a rich fabric of worlds and characters, and he drives his plot with powerful moral philosophy. I love this series because it is one of the most original and compelling I've ever read. Lyra's strength and bravery make her journey from innocence to experience both beautiful and heartbreaking. Even her parents, Lord Asriel and the vicious Mrs. Coulter, undergo a profound transformation. Very few books inspire you to re-examine your life and your ideas about the universe, but this series inspired me to think about the nature of good and evil, and examine my understanding of morality. Yet, Pullman never lectures--it's the wonder of his story that drives its philosophy, instead of the other way around. Everyone should read these books.
3. Harry Potter, by J.K. Rowling
This series may have saved children's publishing single-handed. Beloved by millions for a good reason, Rowling creates a wonderful fantasy world full of awe, but also danger and pain. Harry, Ron, and Hermione are complicated but lovable characters, and Rowling beautifully depicts their deep friendship through many trials. If you have only seen the movies, try reading the books. I enjoyed the movies, especially the last two, but the books give a richer portrait of the world and relationships of the characters.
4. Kushiel's Legacy, by Jacqueline CareyWhile Harry Potter and His Dark Materials are written for children or young adults, Carey's excellent series is very adult. She creates a beautiful, complicated world of fallen angels, where prostitution is a sacred calling. Yet, although the books contain erotica, the bulk of the stories are exciting adventures, more of a spy novels than romance. Her heroine, Phedre, uses any means at her disposal to protect her country and the people she loves. Gifted, or perhaps cursed, with the ability to feel pain and pleasure as one, Phedre journeys to hell and back, only surviving because of her unique abilities. Far more well-written and engaging than the irritating Fifty Shades of Grey, this series deserves serious attention from any fantasy readers.
5. The Wheel of Time, by Robert Jordan and Brandon SandersonThe Wheel of Time is an enormous epic fantasy series of 13 books (the last book is due to be released in January 2013). Reading it is an ambitious undertaking, and not for the faint of heart. Still, these books have a lot to offer: an epic plot, a huge cast of characters, and a highly developed fantasy world. True, sometimes the plot seems to go off on a tangent, and some of the main characters get very whiny, but overall I have truly enjoyed reading this series, and I'm excited to finally read the last book.
As someone who loves fantasy books, I know it can be frustrating trying to find an excellent series to sink your teeth into. I'm always interested in learning about excellent fantasy books, so if there are any you feel should be included on this list, let me know.