This is a great framework to consider the definition of "classic" for me although I don't necessarily agree with all points.
- high quality music for me is probably the most important aspect of defining a classic album, but not only that but I believe that at the very least most classic albums in my mind have at least one track that transcends the era, defines a certain point in time for hip hop, etc. I understand that this isn't always the case as less well-known artists may not have had the push of say a Nas, Biggie, Jay-Z and and might not have the same degree of recognition on a mainstream stage.
- On another note, I don't think albums need to be "perfect" in order to be considered classic either. Ready to Die has "Friend of Mine" which I hate, yet I wouldn't say it takes the classic stamp away from that album.
- similar opinions with regards to points 2 and 4. I think that some albums have also been deemed classics not necessarily strictly based on the quality of the music, but also for the simple fact that sales, success on the charts (singles), etc, but they are classics nonetheless. (e.g. Get Rich or Die Tryin', etc)
The one area that I think things get overstated is with the idea of cohesion. What makes an album cohesive "thematically cohesive vs. sonically cohesive"?
- For instance, Illmatic for me sounds like a collection of random songs, but I don't think that keeps it from being classic.
- Does having the same producer on the entire album provide sonic cohesion? Does making an entire album about a certain topic make it thematically cohesive?
- Do we overlook lower-quality tracks because they fit into the theme of an album?
In summary, I think there are classics that are labeled so because of the quality of the music, the amount of success that they had, or some combination of both.