The world of erotic games is like trying to find gold in a pile of- subpar gaming, shall we say. So when I came across the game Slave Maker, I was pleasantly surprised that an ACTUAL game was made with erotica at is main focus. Slave Maker is a play on 'Princess Maker', a game I am not familiar with, but the idea is that you are a Slave Trainer who takes commissions to train girls as slaves.
It is an interesting game of numbers where you set your slaves-in-training to various tasks to raise stats like Cooking or Sensibility. Of course you also train them to become superb sex slaves, which honestly is the main point of the game. Everything from bdsm to breast enhancement, hermaphrodites and demons, tentacles as tons of other kinks can be found in this game to enjoy. Most of the characters are taken from various anime sources, so familiar faces for those of us who like some Japanese media may be available to play with in it.
As far as outright 'action' goes, well, I haven't found many erotic games like that to speak of. It's a numbers game with sex and decisions and interesting opportunities. The maker is still creating it with many updates in their blog, linked below, so I'd recommend checking it out and downloading it if you are wanting to give being a Slave Trainer a shot!
K Fox and the Magic Sword
Right, so remember how I said there were hardly any erotic games worth mentioning involving action? Well, this is perhaps the most notable exception. This is a fighting game with the lovely Krystal from the Starfox series. She has quite the furry-following online, so it really doesn't surprise me that she'd take center role in an erotic fighter game.
In this game, Krystal has crash-landed on a planet inhabited by lizard people who think the blue fox is quite the catch. It's a fight or get fucked world, and there is a lot of fucking going on in this game. It doesn't have the greatest graphics nor is terribly long, but it is quite the accomplishment in the world of erotic gaming in my book. Kudos to the developer(s)! It's a good time-waster, so if you are ever bored and horny go give it a shot.
Monster Girl Quest!
This is hands down by far the greatest erotic game I have ever played. Ever. Monster Girl Quest has a deceptively simple plotline - young male hero goes off to fight the female monsters in order to defeat their leader and bring peace to the world. Oh yeah, and the female monsters love to rape men into submission, or in order to eat them. It's a turn-based strategy fighting game where you, the hero, must do battle with these seductive beasts who, upon defeating you, like to have their way with you in very long cut scenes...
But the simplicity of the game presented at the start is deceptive. Above any other erotic game this one actually puts a great deal of time and effort into creating an actual plotline - and not just a pornish plotline, but a legitimate make-you-think plotline. The hero Luka soon encounters a mysterious lamina (half-snake) woman named Alice who joins him on his journey under mysterious pretenses. And throughout this journey the ideals of both characters are challenged not only by the trials they face but by each other as well. Not to mention it is heavily humorous as well, it is surprising that amidst all the humor and sex and ridiculousness of that world that it still pulls off great character development and endearing scenes.
There is a great score throughout the game, and though the combat feels like it is on rails for a time, it soon takes off into actually making you think how to proceed if you don't want to lose. And that's another thing - you'll find yourself losing on purpose just to see what would happen! Since every time Luka fails to defeat a monster girl, it has its way with him. Some of them have quite the focus on breeding as well...
Overall, I would highly, HIGHLY recommend giving this game a shot! It is a fairly large file, nearly half a gigabyte, and the link I'll give is from a torrent site with the English version requiring BitTorrent or another like-program, but I assure you that if you are at all into monster girls, forced sex (female on male), or just are looking for a refreshing erotic game, you cannot go wrong with this gem.