If you look at the "classic" bands (like many of those listed already), they all seem to be about pushing the envelope: Sabbath, Motorhead, Priest/Maiden, Venom, Celtic Frost, Death/Possessed (and then Morbid Angel, Deicide), Bathory, the Norwegian BM scene and so on - these bands became known not only because they were proficient songwriters/players, but also because they "kicked it up a notch" from what had come before. After '94-'95, with Death Metal becoming a household name and the initial explosion of Norse BM reaching its apex, everybody seems to have floundered. Now there's lots of exploration "within" genres, but not a whole lot of ground to cover beyond those genres. People have experimented with industrial influences, folk music influences, jazz style stuff and all sorts (even this awful "electro-metal" that came out about a decade ago, with dubstep and dance influences), but nobody really knows where to go to push "metal" to a new extreme. So that's why we're seeing a lot of retro bands rehashing sounds from the past - we're plumbing the depths of what has been revealed by forerunners, while those forerunners are all lauded as "classic" bands that produced "classic" albums - and quite rightly. We'll never have another Altars of Madness, even if someone creates an album that is equally as good in that genre - precisely because Altars of Madness was released nearly 30 years ago. A new Altars of Madness might be a great album, but it won't be "classic" because it's already been done.
I'm a composer, so this is a pretty interesting topic for me. I'm not satisfied doing what everyone's done before, but I can't deny that I have to base my music on what people have done before, to whatever degree. So I'm personally trying to find "grey areas" in between genres that haven't been looked at totally - like incorporating the heaviness of death metal into a speed metal context, or pushing the "pagan black metal" idea further than it's been taken (again by incorporating e.g. more Venom influence than Bathory/Norse BM). But it's very hard to look at the wide range of metal genres available today and think "hmm, how can I evolve this?" Because you can't go heavier on the distortion - that's been done; you can't go heavier on the vocals - that's been done; you can't go faster on the drumming - that's been done; you can't go more extreme on the lyrical themes - that's been done. On and on and on, whatever you think of, it's been done - there would appear to be no more envelope to push.
So maybe now we're at a point where, instead of helping the genre to evolve, we need to be looking at bands that really encapsulate what metal's about, whatever their genre of choice is. "Classic" albums from the past couple of decades will likely be those that didn't necessarily invent anything new or "overcome" their predecessors in terms of heaviness, extremity, power etc., but will be those that stood shoulder-to-shoulder with the albums we know as classics today, and shone a different light on the path that metal had already taken by the time they came to releasing their record. I don't agree with people who say that "metal is dead", since humanity is pretty much fully-evolved (contentious, I know), and we ain't dead yet. Stagnating, perhaps, but we're still around, and some of us are doing cool stuff. I think it's the same with metal. In between the cracks, there are bands here and there - known or unknown - that are doing very good things with the tools that were unveiled for us by the "classic" bands of the past, and time will tell which bands those are (and which albums). Eventually, quality will overcome quantity, and thousands of ok-but-not-great albums will be forgotten in favour of one or two extraordinary albums from any one year in any one genre.
(Oh, and another thing - mainstream attention. Metal didn't become a mainstream genre like other outsider genres in the '80s and '90s - the media tried to bring it in, and things like Nu Metal, emo etc. happened (which did get news reports), but by and large, after the Death Metal explosion of the turn of the '90s and the Norwegian Black Metal "mafia" of the early '90s, the mainstream media basically gave metal the finger and said "do it on your own". Priest and Maiden got a lot more exposure in the '80s than Rhapsody and Averse Sefira did in the '00s. Nowadays you'll only see a metal band on mainstream media if the singer's girlfriend got sacrificed to a pet goat or something (or, alternatively, accusations of "nazism" etc. can still bring the press). The shock value is all that there is for the media, so they won't report on musicians just doing their thing. Maybe that's down to the Norwegian BM scene. But it seems harder for good metal bands to get the attention they deserve nowadays - metal in general, too - because there aren't any decent rags picking up on them. Terrorizer's just died a death here in Britain, used to be one of the biggest extreme metal mags in the business. Now everyone's online, the online metal news is often selective because there's just so much to look at, and a lot of newcomers to the genre have no idea where to hear about what's good and what's bad outside of the first few links on Google. So I think that has a part to play too, if only a small one. No attention from outside of the metal community.)
