It's easy to obsess over the male gaze and female objectification, but of course the pleasing and arousing power of nudity cuts across all genders and sexual orientations.
A 2007 study from the Centre for Addiction and Mental Health and the University of Toronto applied rigorous study to our genital responses to both sexual and nonsexual nude footage, both human and non-human.
Unsurprisingly, they found that both sexes responded weakest to nonsexual nude exercise footage and strongest to intercourse footage. They found that women were generally less concerned with the sex (or species) of the individuals in the videos and placed more importance on the level of depicted sexual activity.
Unsurprisingly, homosexual women responded more to nude females exercising and masturbating than to nude males, while heterosexual women responded about the same to both sexes.