I think it was J G Ballard who shocked an audience of SciFi enthusiasts by stating that "90% of Science Fiction is crud." When the murmur of shock had died down, he continued. "90% of everything is crud." and everybody relaxed and laughed. I think he grossly underestimated the amount of crud, but I think of this when I read a book or listen to music. Will this still be read/listened to in 200 years?
By that criterion, very little modern music can be adjudged classical. The Beatles, Arvo Pärt, Phillip Glass, Vangelis, ... Add your name to the list.
It's even worse with literature. Of modern authors, I think I'd put the Swedish author, Marianne Fredriksson, on the list. Probably Diane Setterfield. I'll have to think long and hard to find more names.
But one name is already up there, as the definition of a classical author, and in particular for one work. It has been filmed innumerable times, it has been made into several quality TV miniseries and at least one crappy one, it is read in its own right and is one of the most popular books in any bookstore, it has been spoofed with a zombie version, and sequels have been written, and there is even a film about its fans.
Of course I'm referring to Jane Austen's "Pride and Prejudice", and however you may say that it was its time's equivalent of Mills & Boon chicklit, there's no getting away from its being a classic by any definition.
And I say that with the full strength of Robert A Heinlein's support: "If you can't measure it, it's not science, it's opinion."