03:20 PM on 11/20/12
To me a classic is a record that completely shifts the musical climate of the time. Even if the record wasn't necessarily the first album to sound like that, it for some reason (in lots of occasions it is an individual song) was the first to garner wide spread attention and shift the majority of peoples musical taste in that direction (Eg Enema, Dookie, Nevermind). Saying that however, since the start of the internet it is really hard to pinpoint which record was the true pioneer (especially in the scene, where radio play doesn't exist for the most part) as in most cases a lot of records emerge at the same time that are generally the same sound, so the "classic" record changes among different areas of people and different groups of friends.
For example in 2002, when the scene started its shift from pop-punk to post hardcore there was a lot of records that came out that made that it happen (The Used, What it is to Burn, Tell All Your Friends, Box Car Racer, The Illusion of Safety). For me I would say Tell All Your Friends is the classic record as thats the one that me and my friends related to the most, but for another group of people it may have been another record.