The New Yorker had short article looking at seven fantasy books you might read after finishing off the well-known staples of Harry Potter and The Lord of the Rings. You can find the list at Seven Essential Fantasy Reads: Going to Second Base: The Book Bench : The New Yorker. (As an aside, I think I’ve read all of these, apart from “The Name of the Wind” which I’ll go an hunt down).
Setting up a ‘definitive’ list of books or an anthology can be a fraught process though. For example, see the recent reaction to ‘The Mammoth Book of Mindblowing Science Fiction’ (see also: Making Lists: Mindblowing SF by Women and People of Color).