Ayvuir said:
I think it's very hard to make a game that is simultaneously a good game and good hypno-fetish content.
I very much agree with this because, the thing is, in my case, when I play a hypno-themed game, it's because I want some interactivity, not because I want some challenge like when I play regular games, so whenever I find that I need to grind, or fight or go to quests before getting the next hypno scene, it does get very annoying. As implied, this is the opposite of what I want when I play regular games, so yeah, what Ayvuir said is right on spot. It's possible that that's just me, however, and probably there are hypno-fans who don't mind having some challenges and then a hypno scene as a reward. But as Origamiswami said, it's best if the hypnosis/mind control are part of the gameplay itself and not just the reward.
One type of challenge that doesn't bother me as much in a hypno-game and that, in fact, I actually sometimes enjoy a lot, is when it's about figuring out how to get your target under your control. I've always loved stories where the mind control element has clear powers and limitations, and the controller needs to play it smart to figure out how to achieve their goal with what they have. Examples range from Thrallworks: Orientation, in which you need to carefully decide where to lead the conversation and find the perfect moments to record the neural activity when you think the subject is feeling the emotion you want; to Nano-Control, in which you need to find a way to get your targets to take a drink with the nanobots in it. The latter does ask you to grind, though, but a similar general concept could be pretty cool if improved upon.
Oh, and also, like Hypnoshadow said, do very much put emphasis on the facial expressions and the hypnosis/mind control itself.