Good call on putting Angel Dust from FNM on the list. It influenced the nu-metal sound of the late 90s and 2000s. The album was way ahead of it's time. Unfortunately it inspired garbage like Korn. But they also influenced some decent bands like Slipknot and SOAD. I'm not sure how Slipknot's first album makes the list though as you're still missing A LOT of albums that meant more to metal than that one ever will.
Here's a few more to add:
Metallica - Master Of Puppets (honestly how did you forget this
Anthrax- Among The Living
Black Sabbath - Black Sabbath, Master Of Reality, Volume 4, Sabbath Bloody Sabbath and Sabotage.
Yes, all those Sabbath albums are that important