Looking at what happened in the 90's, we could consider 1990 to be classic metal's "heroic last stand".
Mmmm not quite... The first half of the decade was still really good when it came to some classic metal releases
1991:
Mettallica - Metallica (although I don't like it it's probably the metal album that sold the most ever)
Overkill - Horrorscope
Anthrax - Attack Of The Killer B's
Gamma Ray - Sigh No More
Ozzy - No More Tears
Coroner - Mental Vortex
Dark Angel - Time Does Not Heal
Voivod - Angel Rat
Motorhead - 1916
Skid Row - Slave To The Grind
Armored Saint - Symbol Of Salvation
Fates Warning - Parallels
1992:
Black Sabbath - Dehumanizer (it was kind of a letdown for me, but it was the Heaven And Hell line up reunion)
Dream Theater - Images And Words
Holocaust - Hypnosis Of Birds
Mercyful Fate - Return Of The Vampire
WASP - The Crimson Idol
Testament - The Ritual
Megadeth - Countdown To Extinction
Marty Friedman - Scenes
Kreator - Renewal
Iced Earth - Night Of The Stormbringer
Manowar - The Tryumph Of Steel
... and of course Fear Of The Dark (although I think it's Maiden's worst record)
1993:
Mercyful Fate - In The Shadows
Motorhead - Bastards
Gamma Ray - Insanity And Genius
Fight - War Of Words
Voivod - The Outer Limits
Overkill - I Hear Black
Anthrax - Sound Of White Noise
Annihilator - Set The World On Fire
Savatage - Edge Of Thorns
Angra - Angels Cry
... and live albums by Maiden, Slayer, Metallica and Dream Theater
1994:
Megadeth - Youthanasia
Dream Theater - Awake
Slayer - Divine Intervention
Testament - Low
Queensryche - Promised Land
Overkill - WFO
Helloween - Master Of The Rings
Mercyful Fate - Time
Savatage - Handful Of Rain
Running Wild - Black Hand Inn
Fates Warning - Inside Out
1995:
Iron Maiden - The X Factor (don't care what people say... it's a great record)
King Diamond - The Spider's Lullaby
Blind Guardian - Imaginations From The Other Side
Ozzy - Ozzmosis
Kreator - Cause For Conflict
WASP - Still Not Black enough
Dream Theater - A Change Of Seasons
Motorhead - Sacrifice
Running Wild - Masquerade
Van Hallen - Balance
Iced Earth - Burnt Offerings
Virgin Steel - The Marriage Of Heaven And Hell Pt 1
Coroner - Coroner
Gamma Ray - Land Of The Free
... and live albums by Testament and Overkill
Just to name some. As you can see there was lots of quality Hard Rock/ Heavy/ Power/ Thrash metal albums coming out.