I know that in Fable I, the screen goes black and you get some really cheesy audio of her saying she’s enjoying it, and then you get up wearing your underpants with the game clock advanced a couple of hours. It’s clear that they didn’t get Meg Ryan for any of the voice acting, put it that way.
Unless I completely misread your post, I assumed you were trying to see sex in a mainstream video game.
My post, which seems you completely misread, meant that because of the high amount of video game sex available already, there’s almost zero possibility of seeing it in a “regular” game.