Timmer wroteBut okay you're probably right. Though Orchid is from '94 😛 it is probably only a classic for the fans. Maybe not their most groundbreaking album, agreed. I guess the same applies to divine wings & paradox: they were defining moments for both bands, but maybe not that special as a whole
Opeth has never produced anything remotely groundbreaking. Though I enjoy the band, they are in no way groundbreaking. Plus, their recent three records ranged from mediocre (Blackwater Park) to bad (Deliverance) to pointless (Damnation.)
As for the666th:
Priest: It'll show eventually.
Kreator: See above.
Opeth: Opeth never wrote any classics.
Nevermore: Dunno, someone else'll have to answer or write that one.
Blind Guardian: Probably.
Dark Tranquility: The Gallery is their only classic.
Rage: Possibly.
My Dying Bride: Dunno.
Dismember: Eh, there aren't many true death metal classics. Morbid Angel wrote a couple, Obituary wrote a couple, Suffocation wrote a couple, Cryptopsy wrote one, Unleashed wrote one, Grave wrote one, and that was about it (unless you consider Slayer and earlySepultura to be death metal, which they aren't).
December Flower: Don't know nothin' bout Crimson Glory, personally, so someone else'll have to answer that.