Sure, but I'm talking about an obsession with boobs, not just with liking them.

Not everyone, about half of human population would prefer male chest to female chest.

No, generally speaking everyone is, else you starve as an infant.

Maybe this is late night and I need to get some sleep, but you seemed to solve a big mystery for me. Almost all of my girlfriends either freely admire another woman's breast/body or showed a great deal of jealousy. I felt they were a bit bisexual but this makes a lot more sense.

Preference seems unrelated to respect. As a ~straight male I prefer female breasts but I can still respect a chiseled male chest.