
Longevity.
I think it's that simple. If an album can be played years after it dropped, and appreciated on the same level as it was initially, that's a great album. That's art. Standing the test of time is really what separates music these days. Lyrics and production can end up dated, but if your album is so dope that it still rocks 10-20 years later, regardless of the sound, you've got something special there.
.. Some songs I'm skipping on what I would call classic albums