If we accept the idea of video games as an art form, the introduction of sex and nudity into the medium seems inevitable when we consider the historical precedent. All artworks and artistic expression throughout human civilization have featured these at one time or another. For one thing, the human form is perceived as beautiful and the sex drive is biologically intrinsic; for another, it's natural to want what one can't have, and these things are generally taboo or restricted; and finally, there's something fun and even funny about the sexual act. Add interactivity into the mix, and you've got yourself a natural match-up.
Presented for your consideration: two articles on the phenomenon, by professional web pundits - one of each gender.
Sarah Crisman: Sex and Nudity in Console & Arcade Video Games. A well done, if sprawling and workmanlike treatise; Crisman packs a lot of good details in and keeps her focus on the consoles, eschewing the computer software field for the nonce.
Sean Reiley: The Top 10 Naughtiest Games of All Time. Graphically rich and creative presentation, using imagery clipped from the games themselves. "Seanbaby" apparently has a reputation for being excessive... er, expressive, and that is evident in his diction.
What to make of the differences in the approaches used here? It would be easy to interpret these pieces in particular ways... for instance, the latter's lurid title seems to play to the idea of male competitiveness and desire for the "extreme," while the former reads more like a thesis. The Crisman article does not shy away from controversial material, but the Reiley piece outright delights in it, indeed, the warning on the first page about what is about to be seen is more cautionary than necessary (and includes an ironic nod to the idea that violence is more acceptable than sex in US culture.)
Since it's impossible to know the mind of these authors, I recommend simply reading and enjoying their windows into gaming history.