Let me breakdown why a classic is a classic,
In any area of media books, films, music, certain things will hit a chord within you, it will speak volumes, what this is, is the subject matter of what was made then, is relevant now. It has to come from that conscious part of you, that wants to connect to everyone, to me people like Dre are Hollywood celeb's, they're about the money, record sales, and maintaining that, what changed after the 90's was the way Hiphop has been explained, kids getting into it think this is it, they don't have a clue who Kool Herc is, or anything about the block of flats on Sedgewick Avenue. The Industry has tried to morph the origin's of this whole movement.
Star Wars:
Basic story of good overcoming evil, but also the playout of a dictator ship ruling everything, that is a timeless feeling we all can connect to in some manner, because none of us want that. Focus on a balance being brought in.
Lord Of The Rings (books)
Again same as Star Wars basically, rid evil and bring in balance.
Harry Potter (Books and Films)
Same story again bring in a balance.
John Lennon - Imagine
Bringing in balance
Pharcyde - Runnin
No elves or Jedi's or wizards, but the message is balance
Classic's usually need this character to them, you do get the freak genius moment of an Instant Classic, but given time it usually proves to be some sort of evolution.
It is also something that can change each time you read, listen, or watch.
Check this video out, some decent knowledge in here,
http://www.youtube.com/watch?v=2CH6af90Ig0