Now that you broadly categorise it as Metal, I don't have an answer. With all the sub genres followed by their multiple sub-sub genres!!
I would have liked to believe (like I did as a kid) it's the aggression, but why would I listen to Doom, DSBM, Symphonic, etc then? I love to listen to Black Metal when I'm depressed or feeling low. I can't think of anything better to do at that time. But then when I'm all "happy-happy" I listen to Edguy for hours! Power Metal is more in your face and aggressive than Death Metal. Many may disagree but who cares. The forum is back. We can fight and abuse each others dead relatives and buy each other beer at the next gig.
So it's my current mood that decides which way I wanna go. Not my general appeal towards metal. Classical Music FTW!
Sorry I don't think I made a point or helped your topic. Just spoke my mind perhaps.
PS - Listen to some good metal www.myspace.com/1833ad