Are big butts really that attractive?

I mean, more cushion for the pushin', yeah. But come to think of it, most of the world's most desired women are skinny and not curvaceous at all (Megan Fox, Jessica Alba, Angelina Jolie, Adriana Lima, Gisele Bundchen, etc) and as for the "bootylicious" women like Beyonce, JLo, Kim Kardashian, they receive much less "hot" ratings by Men's magazines.. So what's the deal about big butts? Is it just another ghetto hype made prominent by porn and rappers?