I'm a very straight attractive guy, but I think penises are much more visually aesthetically pleasing than vaginas, and most people will concur.
Penises are sturdy, they are powerful and strong. There is a lot of nuance - the veins, the colors and the texture. Circumcised ones are definitely more anesthetic than the hoodies. They are built to conquer, and you can tell the strength of a man from a look at his penis.
A vagina? Folds upon folds for no good reason, stained by periods and built to be conquer and to be desired - not for desiring. You can't tell the tightness or fertility of a woman from the sight of her vagina.
Again, I am 100% straight and have only dated and made love to women. A good analogy, penises are something I admire as a work of art, but a vagina is what I make love to.