Dunno man, the 90s brought us Death's best work, the good Cynic album, Nile, some cracking (and cracked) black metal... lot of dross too, of course, but it's the last seven or eight years that've proven a wasteland for me.
Opeth - Blackwater Park.
Slayer - Seasons (1990).
Megadeth - Rust in Peace (1990).
Fates Warning - A Pleasant Shade of Gray.
Spiral Architect - A Sceptic's Universe.
Dream Theater - Awake.
Emperor - Nightside and Anthems.
Soilwork - Chainheart Machine.
Morbid Angel - Domination.
Dissection - Storm of the Light's Bane.
Gorguts - Obscura and From Wisdom...
There is always nostalgia for the ground broken in the 80's, but the 90's yielded many great bands' best.
Ulver - Bergtatt
In Flames - The Jester Race
Meshuggah - Destroy Erase Improve
The 90s hold so many good and interesting directions for metal!
Dark Tranquility - The Gallery
At the Gates - Slaughter of the Soul
Edge of Sanity - Crimson