+1 for Dune and LoTR.
but my favorites are:
A Song of Ice and Fire, by George R.R. Martin.
Martin writes midaeval fantasy in a way that is simultaneously realistic and fantastic. He is an avid historian of the period and so his characters and setting reflect the age, although they use a more modern dialect in most cases. What makes him most interesting though, are two unique points:
His mastery of symbolism. He includes flashes of prophecy and icons which have, at first, one important meaning, but as the story unfolds, you begin to see multiple representations, most notably with the title. Without giving much away, I will say that the "song" of "ice" and "fire" can and does represent both a literal song, a song of steel (battle) between two opposing forces, and the central relationship of two people and their "dance" of relation.
Secondly, his very unique storytelling. Martin does not have a main character, and there is no hero nor evil archenemy. Instead, chapters unfold from different character's perspectives. Each has their own view of the world and events. For example, a soldier's chapter would be told at face value, and probably not take in much detail or social implications, he tells it short, crudely, and from a strategic perspective. A little girl on the other hand, might tell her chapter from a fanciful, dreamy perspective where knights are always chivilrous and daring, and everyone can be trusted. Martin never gives an omniscent perspective, you piece the truth together from comparing and contrasting their views. Each character is not "good" or "evil", they are all varying shades of gray instead of black and white. They have their own goals and desires, and work against and with each other to further them. This results in a great canvas of storytelling in which you root for your favorite team, as it goes. It's full of intrigue, sex, war, philosophy, comedy, - Martin leaves nothing out. Because his characters are believably real and make mistakes, his story takes on a very real presence as you read it, which makes it my favorite series.
The Book of the New Sun, and Litany of the Long Sun, by Gene Wolfe.
Wolfe's New Sun is an amazing allegory. Set aeons into our future, when planet Earth is only known as Urth among many other distant worlds, and the sun has entered its final phase before death, Wolfe writes the story of a Torturer. His world is an extreme prediction of what humanity will do, how we have advanced far beyond any current technology, but that these advances are only available or known to the elite of society. The peasants on the other hand, live in the ruins of that shattered glory age of humanity. Their life is very similar to what we experienced around 1600. Juxtaposed with this are the flying vehicles, laser weapons, and interplanetary gates that the ruling force possesses.
In the story, the main character belongs to a torturer's guild, whose job it is to receive instructions on what punishments are to be carried out, and do so. He quickly learns that his heart holds other desires, and is expelled for showing mercy. Thus begins his wanderings and his journey away from his society, and yet towards it in a larger sense. Wolfe tells his tale using dialogue, poetry, a playscript, historical documents, and every other medium of literature. It is a praise of human art, echoing relics of our past, and theirs, which is our present and future.
He also maintains throughout the book that he merely translated it, and did not invent it. This is curious considering also the theme of time-travel that the ruling class possesses. Although it is never outwardly stated, it is implied by the existance of a character who cannot remember his past, but appears (to the reader) to be a person from the 20th century. Also, certain events at the end of the book have some effect on those in the beginning. Thus Wolfe explores humanity through the hallways of time, past, present, future, and writes a beautiful story whose crowning moment is intensely spiritual.
Long Sun continues in Wolfe's style, which appears to be set in a vast space colony. The inhabitants are unaware that they float in the cosmos, they see only their city, their lake, and other cities which are far above them (on the other side of the cylinder), and the "long sun" that gives light for half the day. In this world, Wolfe creates a story in which the main character, an unbelieving priest, is visited by a vision of a "god" through a "window", which appears to the reader to be a mechanical tv-screen like device. The story follows this man as he searches out, instead, another god, who he believes charged him with discovering and telling people of the more important and possibly more real god who exists even beyond their cities in the deep darkness filled with points of light. In this world, the people use little metal and clear plastic "bits" as money, which are broken off as pieces from a "card". These cards are clear plastic squares with metal labyrinths etched across their surface. I find this story to be my second favorite, as it chronicles first skepticism, and then geniune wonder and discovery, following this character in his quest for the unknown, when humanity has all but forgotten its past.