I'm 37, and started listening to metal in probably 1990. So i grew up on older stuff. I'm a sucker for the classics of most subgrenes before the 2000's. Could never get excited about all the xxx-core bands, or these american kids that rip of all my favorite euro metal riffs from the 90's, but with some "Core" guy singing illegible tough guy or even worse "sensitive tough guy" gibberish over it. Never liked the "Adderall metal" of the late 2000's where everyone was trying to "out tech" each other in tasteless ways. Dillinger esacpe plan was kinda sweet, but all those bands that came after them,
<----me
for me its all about:
-NWOBHM (diamond head, venom, angel witch, etc)
-early American thrash (big 3,etc)
-90s European melodic death metal (in flames, bodom, dark tranquility, opeth, early arch enemy/later carcass, etc)
-90's European back metal (burzum, early Ulver, dark throne, early mayhem, early dimmu borgir, emperor, immortal, even going back to bathory)
-80's and 90's american and euro "traditional" metal bands (i.e ozzy, dio, maiden, motorhead, priest, helloween, accept, scorpions, sonata arctica, early stratovarius, early iced earth, etc)
bands that broke post 2000's?
Mastodon, Gojira, Agalloch, maybe a half dozen others if that.
Metallica and Iron Maiden share the title of GOAT. Greatest of all time, as the hip hop guys say. no bands will ever be as big, or as influential, despite YOUR opinion of them. The size of their success, brand, fan bases, etc speak for itself. no one will ever get to that level again, and rightfully so. Both bands have had some sizeable failures in their careers too, but it doesn't seem to effect their draw, or how passionate their fans are.
my top 10:
1) metallica
2) opeth
3) maiden
4) Bodom
5) in flames (90-2004)
6) Dimmu Borgir (1994-2004)
7) Accept
8) Agalloch
9) Death
10) Hypocrisy
i almost don't consider motorhead a metal band as much as a rock and roll band on speed. but if they're metal to you, then they're in the top 5.