I'm going with the 80's stuff, too.
Why?
Well, for me it's because back then, the metal sound was pretty much "new" and "fresh". But with the modern stuff, it all just sounds the same. The modern stuff sounds too much like old stuff, which makes it boring to me.
Even though I can think of a few exceptions, most modern metal is either boring, or even worse, took metal in a bad direction (listen to the stuff coming out of Scandanavia right now where they mix metal sounds with female sopranos singing like in opera; now THAT is really, really, REALLY bad!).
Anyway, I think metal pretty much reached it's peak back in the 80's and either hasn't evolved since then, or (in the case of those Scandanavian bands) has evolved in a very wrong direction.