A 2009 article from The New York Review of Books. An excerpt:
What is a “classic”? Is it simply (as Frank Kermode, I think, once put it) an old book that we still read? Or is there something a bit more sinister to the whole idea? An old book you feel you oughtto have read? Or is it more casually serendipitous: An old book you have rediscovered and want to share with the world? And what does a “classicist” (in the Greek-and-Latin sense of the word) have to contribute to the debate?
See partial answers at the above link. Some of the comments are even better.