It appears to be same with most of "extreme music". You see the USA grinders a'la Terrorizer playing for couple guys. VON or whoever. When Darkthrone played in Lahti, I don't think too huge audience in local youth house in early 90's.
There was occasional "revival" on genres, like punk shows of mid 90's attracting locally 400 people. Now if you can get 100 for weekend hc/punk show, it seems great audience. But STILL way better than many of the 10-20 people basement shows.
Top metal in few categories... just to mention few...
technical & progressive (death/thrash)metal:
-Atheist "unquestionable presence" LP bought it when it came out, and worshipped since. It was good to see band gain new uprise, although at the same time old farts get annoyed by everybody supposedly being big fans, although didn't know nor care about band before Relapse re-issues came.
http://www.youtube.com/watch?v=sRhfl8zR-1w&feature=related-Death "Human".. of course early albums always kick ass in field of brutal death metal, yet this is perhaps one more ambitious progressive releases which hardly can be copied unlike their approach on "leprocy" or such..
http://www.youtube.com/watch?v=j8vqGzUlyqEdoom metal:
-Unholy "From Shadows" CD. Follow up to head crushing "Trip To Depressive Autumn" demo, both these utterly unique. Very little to do with traditional doom, though.
http://www.youtube.com/watch?v=Qvk_vs7RUSs-Cathedral first 12" (=demo)and first LP. The good releases before they became much less good. Graverobbing retro doom rock before it became trendy. First 12" is heavy and dark.
http://www.youtube.com/watch?v=bwBE4cY0QLIthrash metal:
-Kreator - basically all albums till Extreme Aggression.
http://www.youtube.com/watch?v=GYL8QJgiIdk-Demolition Hammer both albums. Don't know why exactly, but this pretty much ignored "bigger" band always appealed to me. Especially the merciless drum hammering and great way to deliver lyrics:
http://www.youtube.com/watch?v=kv6XYkF-5z4-Sadus, basically all. Fast technical.
http://www.youtube.com/watch?v=iTTAkxnFDwQDeath Metal:
Immolation "Dawn of Possession", one of darkest and heaviest in USA.
http://www.youtube.com/watch?v=icwNtcmqj8Y&feature=relatedDeicide "s/t", good demo and debut, but didn't care much Legion or most crap that followed
http://www.youtube.com/watch?v=bVKy2Va7Ds0Entombed "left hand path". People of my generation in scandinavia could have not lived without being stabbed in face by popularity of Entombed - which they most definitely deserved. Album that can be listened any day any time.
http://www.youtube.com/watch?v=88okA0LN2YQCarnage 12", perhaps even heavier. Their best track linked below, which later was played as Dismember - who also did couple good albums early on.
http://www.youtube.com/watch?v=IpMJCByK6jUAutopsy all. Not too fond of new album, but original era is pure gold from start to finish.
http://www.youtube.com/watch?v=AGACfUD0M-Q&feature=relatedMorgoth "resurrection absurd", band often despised for their "socially aware lyrics". Guys with CRASS patches on leather jacket etc. But this 1989 demo pressed on vinyl was my first exposure for them. Played this particular track in highschool english class - where students could bring english sung music to be listened in end of class! HAHA!!
http://www.youtube.com/watch?v=VSSKlsTbmZsBlack Metal:
-Darkthrone "ABlaze In The Northern Sky", single most important metal album and the most listened in my life.
http://www.youtube.com/watch?v=MDCMhJXN7g0Beherit "Drawing Down the moon",
promo 1992 was total mind blowing, then came album with pure gold.
http://www.youtube.com/watch?v=3Y8zQSA2qvwGoatlord "Reflections of the solstice". When I heard "Underground Church" from metal radio show, I hunted down the CD. Since then been my top favorite. Band got its huge "rebirth" of interest when for example Nunslaughter and Necros Christos guys started actively worship them and re-issues were made. Unfortunately this sample and re-issues are not the original Turbo music mix, but based on later JL America edition, which is cleaner and more sensible. Original chicken dance - bring back the chickens!!!
http://www.youtube.com/watch?v=KJmNdKhwaFYBurzum "Filosofem" of course so legendary should not even be mentioned.
http://www.youtube.com/watch?v=9Bm-kdLwBVc&feature=relatedVlad Tepes/Belketre split, another band you rather not talk, due all the poser kids intervening to desecrate cult. When you purchased this original CD from small polish BM distributor in times when absolutely nobody wanted to even hear about "black legions", it made such impact, not even the new school black legions fan boy clowns can ruin it.
http://www.youtube.com/watch?v=Ltm15oUTXDwGraveland "In The Glare of Burning Churches". Has Polish black metal ever been done better? Most definitely not by Graveland!
http://www.youtube.com/watch?v=3o0s9DCDKI4viking / pagan metal:
Bathory "hammerheart". This came to local library LP shelves and borrowed it. I had no idea what the fuck is this. Never heard metal like that before, and lets say pagan/viking metal basically starts and stops with Bathory for me. There is very little of what was done really did any good. Most pagan metal nowadays sucks ass big time.
http://www.youtube.com/watch?v=NzZMTMVzbt0&feature=related"artistic" metal:
My Dying Bride first 12", I don't really like anything else what they did. Used to have debut album, but already that was little boring. This is massive:
http://www.youtube.com/watch?v=cLjsmTSgvaE&feature=relatedTiamat - when they were moving away from Death Metal sounds.. before they went all the way into lameness:
http://www.youtube.com/watch?v=_e6Sid3KffQetc
etc.....
I leave out grindcore - as I associate it more with hc/punk. Most of categories could have dozens and dozens of bands to recommend, but in times of youtube and such... following links is so easy.