I’m not a man, but I’ve had many dealings with them over the years. The thing I’ve come to realize is that they’re all different. Sure, there are similarities that run through lots of them, like “prefers football to baseball” but many of them also “prefer baseball to football.” I also bet that when they walk into a Burger King, they will all order different food items. (Some of them don’t even walk into Burger Kings at all.)
So when trying to generalize them, it’s hard to come up with something they all like. I mean, first off, you’re probably talking about heterosexual or bisexual men, but not all of them are. (I’ve known gay guys who really like breasts, too – they think they’re fabulous.) But even among the subset of men who do like T&A, some like small breasts and some like large breasts and some like them “just right,” as Goldilocks would say. And some, like Sir Mix-a-Lot, like big butts (and he cannot lie) whereas some prefer butts, like the rest of the woman, to be sweet and petite.
So you’re talking about a wide variety of people here, slightly less than half the human population, and there are going to be differences across groups and individuals. Perhaps the best bet is to find the guys you like, and ask them how they would prefer a woman to look. And if that answer works for you, you can choose to mould yourself to it, or not.
I think what @lucillelucillelucille might be referring to is this. There is a sort of mathematical beauty to proportions. Also, if you have these proportions, it’s a sort of signal that you’re fertile and will make many wonderful babies, which can be a subconscious thing that will attract a guy. However, we’re more than just math, and we’re more than just fertility indicators, or else I never would have gotten married. ;)