Roger Zelazny's Amber series remains my all-time fave.
The Dune books by Frank Herbert.
Much of R.A. Heinlein's work.
Larry Niven's Known Space books and his others. He also has some great collaborations (Mote in God's Eye, Dream Park come to mind).
Vernor Vinge's Deepness in the Sky and Fire Upon the Deep are incredible single novels.
Brin's Uplift books.
The author's name escapes me but the Hyperion books are great.
Anything by Asimov and Clarke is usually a great read.
Sorry to ramble.
-- GA