Big tits.
As long as I can remember my sexual desires since when I was a teenage were big tits, big fucking tits :)
It is common knowledge that men likes breast because it is something to do with us as babies who were breast fed by our mothers so on an unconscious level we still adore them because they are a source for food. gross aha? :)
But why big?probably cause its a sign of fertility, like in the animal kingdom you can take the male peacock for example in which the bigger and more colorful his tail the more attractive he will be to the female peacock.
I for one like big tits because they are fun to look at, fun to hold while having sex. you can fuck them and they look sexy as hell as long as they are proportional to the body.