Here's my AotY for each year from 1970, with a runner up (or two) following.
Pink Floyd and Yes aren't here, King Crimson is, so I'll include King Crimson

1.Black Sabbath - Paranoid

2.Deep Purple - In Rock

3.Led Zeppelin - Led Zeppelin IV

4.Black Sabbath - Master Of Reality

5.Uriah Heep - Demons And Wizards

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Just did a month-long binge and song-by-song rating on Immortal's discography. Remarkably consistent band, great workout music. Even their 'weak' albums are good.

1.Immortal - At The Heart Of Winter

2.Immortal - Pure Holocaust

3.Immortal - Northern Chaos Gods

4.Immortal - Sons Of Northern Darkness

5.Immortal - Damned In Black

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This is the most unquestionably difficult ranking I could undertake. The # of albums I consider borderline flawless from each of these bands is ridiculous. Over a dozen albums from these 3 bands have legitimate arguments to be considered the greatest traditional heavy metal album of all time.

I have a few rankings that are likely hot takes here
** Yes, I like Dance of Death more than most folks. Title track and Paschendale are both top 10 Maiden songs, and Montsegur is only a small step behind that. Those 3 songs are better than anything on Brave New World to me, but the rest of BNW is better and higher quality.
** Yes I kinda like Turbo. It's silly but it's fun and the guitar work and Rob's vocals are absolutely stellar. That kinda sucks about Ram It Down, it's got some of Priests' best lead guitar work and I don't think Rob ever sounded better, but dear lord, some of those songs...
As for the top 6 albums here, honestly put them in whatever order you want. They're that close to me and mood depending it could change

1.Black Sabbath - Paranoid

2.Judas Priest - Painkiller

3.Iron Maiden - Powerslave

4.Black Sabbath - Sabotage

5.Judas Priest - Screaming For Vengeance

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my ranking of the Big 4s Full-Length albums
Near the bottom , the rankings get a bit more 'interchangeable' because I can't be bothered to specifically discern the difference between turd flavors

1.Slayer - Reign In Blood

2.Megadeth - Rust In Peace

3.Megadeth - Peace Sells... But Who's Buying?

4.Metallica - Ride The Lightning

5.Metallica - Master Of Puppets

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1.Black Sabbath - Paranoid

2.Black Sabbath - Sabotage

3.Black Sabbath - Master Of Reality

4.Black Sabbath - Sabbath Bloody Sabbath

5.Black Sabbath - Black Sabbath

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1.Iron Maiden - Powerslave

2.Iron Maiden - Somewhere In Time

3.Iron Maiden - The Number Of The Beast

4.Iron Maiden - Seventh Son Of A Seventh Son

5.Iron Maiden - Brave New World

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3 caveats
1. Death metal album (not just debut from band that became death metal, like Carcass)
2. Released calendar year 1999 or earlier
3. By a band with more than 1 album (1-album wonder list is elsewhere)

Yes, there are a few bands conspicuous in their absence. For whatever reason, I just never really got into them.
I don't dislike them, but I don't regard them as highly as most folks do

EDIT - I stayed away from death/thrash combo albums, more for convenience's sake. So Malleus Maleficarum, Illusions, Seven Churches, Serpent Temptation, etc are not on this list, but they'll be on the next list I make (top 25 Brutal thrash/death-thrash albums)

1.Morbid Angel - Altars Of Madness

2.Necrophobic - The Nocturnal Silence

3.Nocturnus - The Key

4.Sinister - Cross The Styx

5.Demigod - Slumber Of Sullen Eyes

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1 album per band per subgenre
work in progress, updating as I go through the song-by-song ratings on RateYourMusic.com
I will typically update my black metal faves - https://metalstorm.net/users/list.php?list_id=6924
and my death metal faves - https://metalstorm.net/users/list.php?list_id=6298
prior to updating this one

1.Queensrÿche - Operation: Mindcrime

2.King Diamond - Abigail

3.Voivod - Dimension Hatröss

4.Mastodon - Crack The Skye

5.Lykathea Aflame - Elvenefris

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Immolation is my favorite death metal band by a pretty comfortable margin, so I figured I'd throw my rankings out here.
Note - there are a few album placements here that are NOTABLY different from the average Immolation fan

1.Immolation - Close To A World Below

2.Immolation - Unholy Cult

3.Immolation - Acts Of God

4.Immolation - Atonement

5.Immolation - Majesty And Decay

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almost done, about 10-15 more bands still to listen to

1.Immolation - Acts Of God

2.Heaving Earth - Darkness Of God

3.Artificial Brain - Artificial Brain

4.Esoctrilihum - Consecration Of The Spiritüs Flesh

5.Blind Guardian - The God Machine

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* Updating this as I get around to doing song-by-song on RYM.
* 1 album per band
* limiting this to actual black metal releases, as opposed to releases by bands that were, at one time, black metal.
>> Some bands really do incorporate a lot of both death metal or doom (or avant garde or folk, etc) and black metal in their albums, so I consider them to be 'black metal adjacent' even if it might not be 'purely black metal'

1.Weakling - Dead As Dreams

2.Caladan Brood - Echoes Of Battle

3.Deathspell Omega - Fas - Ite, Maledicti, In Ignem Aeternum

4.Oranssi Pazuzu - Mestarin Kynsi

5.Altar Of Plagues - Teethed Glory & Injury

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Some of the best metal albums ever released have been by bands that only had one full length release.
List is (and probably always will be) a constant work-in-progress.
If you know of a "one-and-done" metal band/album that isn't on my list, feel free to recommend

1.Weakling - Dead As Dreams

2.Caladan Brood - Echoes Of Battle

3.Lykathea Aflame - Elvenefris

4.Timeghoul - 1992-1994 Discography

5.Thorns - Thorns

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1.Ethereal Shroud - Trisagion

2.Veilburner - Lurkers In The Capsule Of Skull

3.First Fragment - Gloire Éternelle

4.Replicant - Malignant Reality

5.Dormant Ordeal - The Grand Scheme Of Things

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My personal hard rock/heavy metal album of the year that I own.
Truthfully, for several years, I just gave up trying to figure out what was in 2nd place (and sometimes, even in 1st).
Some years have so many options....

1.Black Sabbath - Paranoid

2.Black Sabbath - Master Of Reality

3.Black Sabbath - Black Sabbath Vol. 4

4.Black Sabbath - Sabbath Bloody Sabbath

5.Blue Öyster Cult - Secret Treaties

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It's closing in on the end of 2021, so revisiting the year of the lockdown

1.Oranssi Pazuzu - Mestarin Kynsi

2.Akhlys - Melinoë

3.Black Curse - Endless Wound

4.Cryptic Shift - Visitations From Enceladus

5.Draconian - Under A Godless Veil

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