BRizzl3, you apparently don't read books, own a TV, watch movies, or internet videos, do you? Well, I'll enter into this discussion of the mammary nature. First, I'll dismiss you, then I will attend to putting my hand in on this.
Without basis for this it means nothing. A poll, a university study, some kind of statistics.
Marketing analysts have done all this work. Watch any major beer commercial. Check the cover of any romance novel. Look at any billboard directed at one *** over another. You will see quite quickly that Mikhalia is dead-on.
The big problem with your post is that you're talking about which sexual organs are most attractive, yet in your examples you only talk about clothed individuals. If you are going to assess sexual organs than the only fair way to do this is with a nude subject; since you can't view all of the reproductive organs when someone is clothed.
The bulk of your daily interactions, unless you live in a nudist colony, will be with clothed individuals. You can and will be aroused by what you see at times, and therefore you need to get why. I'll go into that in a second. As for finding out why you can get excited over certain body parts over another, no two people are the same. But the majority of guys will say "***" or "Bewbs" long before you will hear "Crotch". Women will say Face, Abs, ****, Shoulders... just about everything except *****.
It seemed like your post was "Why are ******* significantly more attractive on clothed individuals than vaginas and penises?" instead of "Why are ******* significantly more attractive than vaginas and penises?"
Don't watch much **** either, eh?
Ever notice that most of **** STARTS with a clothed individual, that slowly peels for the camera? Yea, I bet you fast forward and never see that. Usually, the tease starts with a woman revealing her ******* or exposing them, then slowly working to other regions.
You also spoke about the appearance of the clothed ****, which you didn't really say was found more attractive by most people, only that it is not as noticeable to most people. Which you also have no backing data for... I think we need a poll, but I don't have premium lol.
Actually, this plays directly in the crotch vs. chest stuff.
OK, first, why is nudity sexual at all? Because it's forbidden. Back in the day, ANKLES could be ****, because most women wore dresses that completely covered them from head to toe. So as society has become more liberal, the areas of sexuality changed until we have the big three that were mentioned.
Now, here's a bit of scientific data that was neglected. ******* react both to temperature and sexual arousal. Woman can flush on their chest just like their face, and there are two places that can likewise represent excitement... or being cold. So they are a visible sign that a male has a shot with a female. And males being visually oriented for their data-gathering, visible signs are welcome.
Now, as for the why people don't stare intently at a crotch as willingly as the **** or chest... that's simple social norms. Let me ask you, if someone who you did not know started staring directly and intently at your crotch, how would you feel? Most likely, unless that was the intent of your clothing choice for the day, you're going to feel uncomfortable. Either you will think they are finding something wrong, or that they have something wrong themselves.
But why not the same feelings for the rear? Weeeeell... none of us has eyes in the back of our head. Say you see a major hottie, but you don't want to be caught staring all creepy stalker-like. The easiest way to check the goods is when they aren't looking. Therefore, you begin to have a growing appreciation of the backside of the opposite ***. And since, again, the forbidden fruit is the sweetest, you stare at the departing end of the crotch, the ***.
You can also toss in the time-honoured argument in the case of the female form that curvaceous woman are more desirable in lean economic times because those curves show that they are successful at staving off lean times, where as thin women are more in vogue for opulent times because it shows a restraint by the woman for not indulging. But then that's more marketing fluff than reality. We tend to desire the type of man or woman that we first became sexually aroused by.