I prefer the female protagonist. I don't self insert.
In porn games it's just fun to see the transformation from somewhat innocent (not stupid, I hate those) to "hey maybe fucking around is not bad at all". Simple. Though at times it really depends on the way the character is. I will not enjoy it just because it's a female, she has to have something to her other than "this is the girl that gets fucked in this game". Give her proper character development. Also, if she's proper hot (for my taste) then I am completely fine with seeing just the one girl being perverted.
In normal games it depends, it's different there, but if I get to create a character it will always be female because I don't fucking know what's a "good" look for a guy, but I know how a badass, attractive lady could be, so I often make one. Believe it or not, it's not to stare at their ass, no (you can though). I also find it easier to actually care about what happens, especially if the game is open world like Cyberpunk or Fallout, where I get kind of protective of them.