Catherine is an incredibly mature and sophisticated game... I need to finish it. Of all things, my girlfriend gave it to me! But above and beyond, I think it would be interesting to see a game that just dealt with the fact that relationships change, especially young relationships. Nothing sinister or amoral even, just two protagonists who's relationship slowly drifted apart. I had this happen when I was younger a few times, it was sad but very honest and realistic. I think it could be done in a not so negative way either, where one or both protagonists find love in other people, and realize that the original romance just wasn't as fulfilling as they thought. I'm sure there are small side examples, and I'm sure there are some exambles where woman are with villain men and fall in love with protagonists, but that usually falls into the "woman getting out of an abusive relationship" description, which is something entirely different.