Wow - I read 4 of them: Earthsea, Narnia, Potter, and Lord of the Rings. Couldn't even begin to rank them because they were transcendent and timeless.

I would add two more that I loved: Susan Cooper's The Dark is Rising and Patricia McKillip's Riddle of Stars (also called the Riddlemaster Trilogy).

Both are more suited to Young Adult - like the others I read in this list - but still superb.