I loved A Thin Red Line and Requiem for a Dream but I don't watch them when they're on. Yet I've actually sat through D.E.B.S. and Accepted more than once.
Many great films aren't to be "enjoyed" the same ways as a confectionary film. Many people don't look to be challenged the way many high minded films challenge them. Hell, many people don't even want to be bothered reading sub-titles. Doesn't mean they can't enjoy a foreign film but 9 times out of 10 they are looking to invest less when watching a film.