It depends with that hip hop you like, with 'underground hip hop' (i hate the cliche saying) it might not be for everyone, but still there are underground classics that fans of 'normal' hip hop might not like...
But in that case, if the overall general consensus from 'underground hip hop' fans is its a classic, if you not a fan of 'underground' its hard for you to argue against it, other than say you dont like that kinda hip hop, it doesnt mean its not a classic, there are classic 'metal' albums that I hate, but it doesnt mean they arnt considered classic... Its like me talking about what 'Mumble Rap' albums are considered classic in away, I cant contribute to that discussion, other than 'no its wack' lol but 'mumble rap fans' can have that discussion...