First, I'm mostly concerned with male protagonist rape scenarios. I think female protagonist rape is more often tied to theme, if that makes any sense. I'm not saying it's better, but it's a bit different.
Second, let's be clear what rape is (just in case). This includes any non-consensual sexual activity including, but not limited to:
"Classic": She says 'no' and you say 'yes.' Can include the victim being restrained against her will.
Unconscious: She can't say no, but she also can't say yes. This includes night time visits and drugging the victim.
Mind Control: She said yes, but only because some outside force is influencing her. Mind control, aphrodisiacs, pheromones, etc. This is often typified by the female being either unaware of what happened or even angry or regretful about what happened.
Coercion: Have sex or else. She said yes, because she was threatened.
Probably a few other scenarios, but this covers a lot of them.
Shortcut to Sex: Basically the dev wants to deliver a sex scene and they want to do it as quickly as possible. So rather than spending time explaining why the woman is consenting to sex, they just use a rapey scenario. You might consider this lazy and it might just be a dev "giving players what they want."
Rape Fantasy: The idea here is that the player is supposed to enjoy the fantasy of taking advantage of a woman. The rape is on purpose because it's "hotter" than consensual sex. This one is more believable if that's the theme of the game like being a slave trainer or some shit.
Doesn't know how to interact with human females: Pretty self explanatory. I feel like it's possible some devs honestly don't know how to write normal interactions with women. Could chalk this up to lack of experience or overexposure to pornography. They don't see why slipping drugs to the girl you like to have sex with her is a bad thing. I like it when an MC gets mad at a guy who is trying to fuck one of their potential conquests. "What an asshole, all he wants to do is fuck her." Right....
(I didn't start this thread to name and shame specific games, just to discuss the topic in general.)
[Late Edit: I'm referring to games where the non-consensual sex doesn't really fit the theme of the game.]
I think you're defining rape broadly enough that just about any form of aggressive sex is going to apply. Lots of people like (I'm sure there is tons of stuff not on my list that are also applicable):
- domination: this would apply to people who fantasize about being the one doing the raping
- submission: yes there are people who fantasize about being dominated and rape is just 1 way that could play out
- mind control: superpowers plus sex? Who hasn't had fantasies of hyptotizing the head cheerleader or whatever as a kid?
- incapacitation: again, this allows sex with someone who would otherwise be out of your league, not my thing but yeah you get turned down, just get her drunk and/or slip her some pills and you're in
- blackmail: who hasn't secretly thought about how nice it would be to blackmail that person who was mean to you into sex?
- revenge: similar to blackmail, who hasn't imagined ambushing their former bully (or his girlfriend) or whatever and fucking them as punishment?
- bondage: usually when I think about this everyone involved is willing, but that doesn't have to be the case
- sadism: yes there are people who like this stuff but I think most aren't really into the hardcore variants (being burned, cut, etc)
- masichism: I don't really understand this one but yes this is a thing too...
- rough sex: Usually when I think of this I think of people who are kind of into a very light form of S&M or bondage. Someone pretends to resist, the other one pretends to restrain them
- humiliation: Again, I don't understand this one either but some people want to be humiliated
- heated sex scenes where nobody asks or gives consent for anything, maybe nobody even speaks, more like just grunts and moans or whatever (this could also fall into the "no means yes" scenario where both are into it and what they're actually saying doesn't matter
Rape fantasies can take bits and pieces of any of those (or all of them) and weave them all together. Someone who is into one or more of those things will probably find something appealing about a rape scene even if it's not specifically focusing on whatever their real preferred kink is. In fact if you use the broadest definitions of consent like some have advocated for use as a standard in sex assault cases (where lack of repeated verbal consent = rape), then the only scenes I like would be considered rape.