Yeah 2001 was the last really good year for metal IMO - at least post-80s power metal and prog-power metal.
2001 COOL METAL
Opeth - Blackwater Park (best opeth - EDIT not fuck that Deliverance. oh well it's on par.)
Ensiferum - S/T (very good)
Green Carnation - Light of Day, Day of Darkness (insanely good)
Windir - 1184 (very good)
Devin Townsend - Terria (crazy fucking good - best [heavy] Townsend)
Pain of Salvation - The Perfect Element pt. 1 (good)
Savatage - Poets & Madmen (good, especially the song Man in the Mirror, fucking masterpiece)
A.C.T. - Imaginary Friends (good, but kind of their weakest effort)
Summoning - Let Mortal Heroes Sing Your Fame (most epic-sounding album of all time)
Finntroll - Jaktens tid (it's really awesome, and their only really good album)
Bal-Sagoth - Atlantis Ascendant (I prefer a later album but this one is cool. not many bands like them)
Entombed - Morning Star (mostly for the song Chief Rebel Angel)
Beyond Twilight - The Devil's Hall Of Fame (this is one of the two albums with Jorn Lande that is actually good)
Ark - Burn The Sun (this is the second one, hahaha! I guess he had a muse this year only)
2001 POWAH METAL
Avantasia - Metal Opera pt 1. (good)
Falconer - S/T (good)
Lost Horizon - Awakening the World (good, insane vocals)
Edguy - Mandrake (their last decent album)
Sonata Arctica - Silence (good)
Kamelot - Karma (hardly their best though)
Adagio - Sanctus Ignis (not too good actually)
Iced Earth - Horror Show (last good album)
Therion - Secret of the Runes (honestly haven't listened too much to this, but IIRC pretty good)
Rhapsody - Rain of a Thousand Flames (one of their best - not that they're super good but still)
Freedom Call - Crystal Empire (CHEESE LEVEL MAXIMUM :: ABORT MISSION :: TERMINATE ::: FAILURE TO COMPLY -- SHIT IS TOO CATCHY :: MAYDAY WE'RE GOING DOWN)
BONUS ALBUMS
Yes - Magnification (The Ladder is one of my favorites, and this isn't nearly as good... but still - Yes)
EDIT: what am I thinking of course it isn't the best. I gotta do this for more years and compare. but I'm pretty sure no year post 2001 comes close. Gotta check like 98 and earlier.
Oh and this is mostly in metal. best year is probably like 72.
EDIT 2: fuck it, this is impossible. I keep finding gems in every year.
Okay so 2001 - best post-80 year for power metal and a really good year.
EDIT 3: if you would have asked me a couple of years ago, I'd say '99 was the best, my top three albums at that time were all from 99:
Mr Bungle - California
Dream Theater - Scenes from a Memory
Dan Swanö - Moontower
2001 highlights (of songs that are probably not as known or highly rated as some other (such at blackwater park which is generally considered very good)!!
Savatage - Man in the Mirror. The perfect metal whisky/booze song for metal gentlemen. Such as myself. And you.
Windir - Journey to the End. Crazy dance part starts at 3:40. I have actually danced to this, once. I never dance. You shall dance, too.
Entombed - Chief Rebel Angel. Raw tribute to Satan. You shall pay tribute to him by listening to this.
Lost Horizon - Highlander. One of the best post-80s power metal songs. I hate the eagle sound in the beginning BUT OH MY UNHOLY DEITY THAT CHORUS OHHuhuhhhhhhhhhhh fucking voice. Oh look you get lyrics too so you can sing like a bitch as well. It's a long fucking song so prepare your throats. "long song", "prepare your throats", hah.