Terry Brooks. Start with the Sword of Shanara. It's a lord of the rings clone, but a very good one. Brooks has written a hugely detailed world that is worth seeing.
Sword of Truth. Yeah. Hmm. The series has some realy shiny parts and some real dulls parts. The first few books are a good, simple story. The middle books get really preachy and (as has been mentioned) Ayn Rand like.
Wheel of Time. Christ, almost everyone will tell you that you need to read them. At least read Eye of the World. See what happens from there.
Malazan Book of the Fallen, oh boy, where to begin. Any discussion about Erickson will quickly make it clear that there are mostly 2 kinds of people in the world. Those that think his books are genius, and you are an idiot if you don't agree. And those that think his work is a tragic pile of dung, with weak character, poor writing, and a plot written buy someone with schizophrenia. If you go the Malazan route. Good luck..hell even the author admits that you either love his work or despise it.
And now for a new recommendation that others might not have made. David Weber's Safehold series. Weber is known for his military science fiction and Safehold is kind of really sci-fi/fantasy. Imagine someone with knowledge of faster than light travel, high tech weaponry, and super robot speed dropped into a 17th or 18th century society. Worth checking out.