Confessions of a Metalhead...The albums I probably should have heard by now, but haven't. Some of them I'm not sure I'll ever bother with. Capped to a maximum of three per artist. Also contains Hard Rock albums.
Edit: apparently I have actually heard Reign in Blood and just forgot about it.
Also check out my blog where I make attempts to address these omissions: http://www.metalmusicarchives.com/forum/forum_posts.asp?TID=16330&title=fixing-the-confessions