A phrase used by pretentious and douchey people to pretend they know a lot about music or to make people think they knew about mainstream music before it was mainstream. To the douchey user of this phrase, it doesn't matter if the older stuff is actually good; all that matters is that it is the older stuff. Many times the person who uses the phrase has never even listened to the older stuff.
Person 1: Have you heard the new REM album, i think it is really good!
Hipster Douche: Meh, it's mediocre at best...but their older stuff is so good!
Person 1: I know what you mean, Document is a great album!
(At this point, the hipster is caught off guard...he has only heard that document is good, but has never actually listened to it.)
Hipster Douche: (In an unsure voice) Yeah man, it's totally awesome!