Back in the 19th century and earlier even commercial literature (Charles Dickens, Matthew Lewis) was good stuff. I believe this can be attributed to the fact that literacy was low in the less educated classes. As more and more became literate, literature dumbed was dumbed down; and look at it today: The only new books on the shelves are Stephen King, Danielle Steele, Jeffrey Deaver garbage. Every now and then there's some book like The Corrections that passes itself off as real literature, when it's actually just REALLY REALLY BAD wannabe-literary fiction that recycles cliches from films blatantly.
I may sound like an elitist, but it would be silly to say that the lower classes have the same opportunities to understand and appreciate literature given that they have less education and less time to read.
Sure there are still great writers like Russell Banks and Salman Rushdie but very few.