Here are my all-time favourites, in no particular order. Each was a fantastic, unique, and special experience from cover to cover. Most I view as masterpieces, a few have sentimental value, and a handful of them changed my life. I can only hope that many more will make it to to this list.
The Silmarillion by J.R.R. Tolkien (my long time indisputable favourite. I would be shocked to find something I liked better.)
The Hobbit by J.R.R. Tolkien
The Lord of the Rings by J.R.R. Tolkien (all three)
A Game of Thrones by George R.R. Martin
A Storm of Swords by George R.R. Martin
Watchmen by Alan Moore
Hyperion by Dan Simmons
The Fall of Hyperion by Dan Simmons
Foundation and Empire by Isaac Asimov
Second Foundation by Isaac Asimov
Dune by Frank Herbert
Children of Dune by Frank Herbert
Memories of Ice by Steven Erikson
Harry Potter and the Goblet of Fire by J.K. Rowling
Harry Potter and the Deathly Hallows by J.K. Rowling
Sunwing by Kenneth Oppel (my favourite as a child.)
FOTS Fantasy 