I've wondered about the original question here myself. Men are big, hairy, unattractive beasts. Women are soft, smooth, curvy, and pretty. Well, not all women have these qualities, but the ones I like to look at do.
But I've looked at myself and other men and wondered HOW women thought we were attractive. It's got to be instinct, as others here have said. Plus we can fuck them in ways their dildos and vibrators can't.