A majority of them all since, like, 7th grade. Black Metal was one of the only things I listened to in junior high and my first year in high school. Naturally, I have heard almost all of the ground breaking albums and than some of the more obscure ones. The only things I do not think I have heard is Arcturus and all of Ildjarn releases(I have only heard Ildjarn-Nidhogg and Forest Poetry), so I think I am pretty well-set to say just such a thing to him.
@Derek: Yeah, you got a while to go before you hit most of the classical albums. I would not say Dark Funeral has released a masterpiece or a 'classic' album in regards to the Norwegian time period, assuming we are including Swedish bands like we should.