I got inspired from the XStoryPlayer progress and some general ideas about rethinking "sex games" as a genre rather than a gimmick or video sex toy. As a freelance developer, maybe I can bounce some ideas off with this thread that hopefully are seen eventually, if not in XSP, then something very soon.
First, some random game theory crap of the top of my head about content:
If a game has interesting, cheap/free, and re-playable content it usually gets popular. Hell, custom content is practically a must for most games. These days, the two best ways to make interesting, cheap/free, and re-playable content is using generative content creation systems and having the more creative players make content that is supported by the developers and can be easily accessed by others and given feedback. Creators love feedback. It creates a lot of "stuff" very quickly and the only developer investment is the time needed to create the systems for generative/custom user content. If you give the player enough creative freedom and don't focus entirely on specific _____ simulations but a more generic group of simple simulations that can easily be tweaked by user input, both with or without them being conscious of it. Then give it its flavor or concept while still giving the player absolute creative freedom in a world that is coherent. I think...
I've never played an Erotica Game. Just Sex games/video sex toys that never gave me any reward or accomplishment (I mean the feeling not the virtual BS swag, but that's kinda nice in a way). Also they lack features that have made games popular for the past 15+ years. "Hako" came kinda-sorta close to having a legitimate reward system and internal renewable content. If you aren't familiar look it up here
http://hgames.wikia.com/wiki/Box_-Hako-. It had an, albeit odd, reward system that let you get more game stuff to play more with. It also had [procedurally generated] girls which added to replay a little. But as with most if not all "sex games" it is about a decade behind in innovation. These days a game has to be simple but give you everything you could want. Sure, fancy Physics and Shaders... but that's something every game should have, more so if you claim any real interactivity. Even if you took all the best parts of Artificial Girl/Academy, SexVilla (with the K17 mods), Bone Town, and every Illusion/Tea Time game and put them together it would still fall short of a true Erotica Game in my mind. I don't think it's technical or gimmicks but rather "game play" that make the perfect Erotica Game. That and variety, like most games.
I'll break things down into four basic player groups and their possible role in Erotica Games as a genre. I'm not trying to ignore anyone but most of the others are hybrids of these.
* Casual: Probably who plays the genre as is... but they should have something that makes the game quick and satisfying, but new each time. Not the same encounter, 4 encounters, or even 10... There are 7 billion people that a person could fantasize about. Not just that but all the fantasy characters that people fantasize about should be considered. A quick fap game feel that has something new each time you play but make it something that maybe I also want to achieve and not so much as a sexual aid. They need something that doesn't require commitment or a lot of time but still gives adequate rewards and variety.
* Hardcore: give them the ability to bang more bitches than HardcorePlayerX. Give them rewards for working hard or make it difficult if they want it to be but make the reward scale for effort/difficulty. These players might be looking for a quick fap game but if it's engaging enough, they may not want to just toss it aside after the fact or even spend time working up to that point. Here's where I think most contenders fall flat in sex/erotica games: They try to make it either too humorous or too technically "pretty". Hardcores need solid game play. They need something that requires effort and gives reward in epic proportions tailored to their skill.
* Role player or Immersion Whore: They want to escape into an interactive story for a few hours. They probably want every detail of every kink there is and they would like to explore and be surprised by many story arcs and objects. This is the player the genre was probably made for but never even comes close to providing for. They need the same variety a Casual player needs but in more cerebral and interactive ways. They need good story where they are the center of it all and they want to feel like they own the experience.
* Creative/Storytellers: They don't play a game they play with a game. They try things out of the ordinary and are more at home with games that nurture the creative streak and allow custom content. The extremists are the Modder and Machinimist types. This is how they play and if you include in-game tools for them they will actually be playing your game to create. The other three players will love them and the developer for it.
More on the creation parts: Imagine being able to drape a soft bodied character with dynamic cloth and cutting out an outfit for other players to rip off. Or creating custom dungeon equipment, even scripting a story line that can branch off other creators story lines and be compatible with other creators characters. Most games have stuff like this! Like I said, the other three love the creator types... They need each other. And this player needs tools and the more native to the game it is the better. Unless you want to get buy on your development team taking on the full brunt of that variety and renewable game play most games have.
TL;DR version: Game play > fancy technical stuff and visuals... but don't for get that fancy technical polish when you've got the meat perfected and don't create something that someone else would be happy to do for free... even if you trick them into thinking it's game play, lol.