I don't want to get too psychoanalytical, but essentially the goblin genre always portrays two main fetishes:
1) A rape fetish that has more mass appeal to a general audience because of the fantasy story elements. This makes the rape feel less immoral to the viewer, i.e., the average player feels less distaste consuming fantasy rape than more realistic depictions of rape.
2) A Power play/dominance fetish; goblin games are 1-dimentional story arcs. Goblins only want to breed, every action in the game leads to this goal, there is no other story. In this sense goblin games appeal to a player who isn't interested in 'dating-sim VN' pornography; the allure of the goblin genre is fast, fappable, content.
I'd say there's also some kind of intrinsic correlation, or relation. between the idea of a goblin who wants to fuck everything attractive around it, and the mindset of the actual player who is actively trying to nut. It's a perverse harmony between the players mind IRL and the game itself.
I feel confident in this analysis because I play and enjoy pretty much all the goblin games out there. *pulls on collar, laughs awkwardly*
I think Goblin themed erotic VNs/ games are all about the humiliation fetish. If several beautiful women are raped and corrupted into loving the abuse step by step by an ugly, weak fantasy critter or a horde of them, it's mainly about humiliation in my book.
A beautiful and desireable, attractive person, who would usually be beyond reach for most, is humiliated, if she/he falls for someone ugly eventually or at least someone, who'd be considered to be very much unattractive for most. In VN's and erotic games or porn comics it's common in various forms like grandpas doing hot and much younger women or fat nerds with glasses and acne doing the same. In the fantasy genre Goblins simply stand for the ugly part.
Goblins are very much the antithesis of the typical fantasy hero, who is usually portrayed as a handsome, strong, tall, loving, caring individual. In fantasy Goblins are ugly, small, nasty, treacherous, weak, therefore coward, use hit & run tactics and ambushs and usually are only dangerous for skilled warriors in large groups. They are clearly not attractive. If they rape a beautiful human or elven maiden into submission and use her as breeding stock, she is of course humiliated foremost.
