Probably the post I agree with the most.
Unless you're Refused.
I'd like to nominate The Shape of Punk to Come as a classic in this thread. Thoughts, go.
This may or may not already been addressed, but one quality of a classic album is going to be if it holds up after its time. For instance, I know refused was gaining brand new fans off of The Shape... On this last go around. Not many of my favorite albums, even though I consider them classics to me, have that same appeal.
That being said, albums like postal services-give up, and sublime- s/t have been bringing new fans to bands that don't exist or at least not in their original "real" form anymore. Hell, crossing genres even Johnny cash is still convincing people to listen to classic country.