i dont think there is really such thing of a best metal, or best any band, really. i just read this entire thread and there were alot of great bands and to each ones own they are all the greatest metal bands. but hey, to hell with philosophical views, i'll just go along with it and the best metal band would ofcourse, without a doubt be my favourite band, because obviously, they have to be the best if they are my favourite, my favourite band isn't gonna be a 2nd rate band now is it?

(i have 3 tiers of favourites)
Opeth <-ultimate

morbid angel, cradle of filth <- top favourites

nile, psycroptic, frankenbok, destroyer666, devolved, omnium gatherum, astriaal, bal-sagoth, deicide, amon amarth <- favourites

then just a shit load of other bands, like napalm death, carcass, slayer, arch enemy, psi-kore, and so on.

my order of 'best' bands