This topic is old, but maybe you're still checking it, or someone else will. If you don't necessarily need hentai, I think Raging Loop (light horror adventure) and 428 Shibuya Scramble ('24' with more comedy and less [sadly] Kiefer Sutherland) are amazing. Steins;Gate obviously, if you're into science fiction. Chaos;Child mixes suspense and sci-fi. If you're comfortable with older games and, therefore, older layouts and programming, 11Eyes and Heartwork are awesome and include some hentai.
I'm currently working through 'Riddle Joker' and 'Fuck Me Royally!'