So, I've been working with observing a theory for a while that is very interesting as far as characters and stories go. It's the conception of the "unattainable, most irresistible woman."
Granted, there are countless different projections on what makes a woman "irresistible," both in media and reality. But across different forms of media, I've found a repeated archetype that has been the most convincing and is most consistent to me.
I'm working across three examples here. Let me know in the comments if you think any other characters fit the mold. The three characters are Brett (Lady Brett Ashley, from Hemingway's The Sun Also Rises), Ilsa (Ilsa Lund, Casablanca), and Denna (from Patrick Rothfuss' series The Kingkiller Chronicle).
The archetype is pretty simple. There is an obvious mutual attraction between the male protagonist of each story (Jake Barnes, Rick, Kvothe) and the given female love interest. They'll oftentimes even share an affair or short-term romance, on-and-off. But it always ends up that, due to some baggage or past secret, she cannot be with him in the end. The clearest setup and resolution to this is with Casablanca's Ilsa. She can't be with Rick because she's married, and even when Laszlo is presumed dead or she has supposedly given up on him, there are clear reservations. But Rick at the end of the film (and, conveniently, resolution to his arc as tragic hero--but that's for another time), is able to give up Ilsa to Laszlow. Though this is perhaps the greatest loss to him, it is the only way for him to be at peace and experience resolution.
There are other elements to this character archetype. I might also bring up Cowboy Bebop's Julia as an example, especially to demonstrate the "run away with me" trope. The difference there is that she and Spike actually run away together, and it is not her intents and character that prevent this from happening as planned. In the other cases, however, it is some hangup relating to each female character that prevents them from running away together. Brett always concludes that she and Jake could never actually be together despite their friendship, feelings, and compatibility--as though it's a missed opportunity. Ilsa discovers that her husband is still alive and has escaped the concentration camp, and she stands up Rick. And Denna veils herself in a vague fear of commitment and ptsd-style reaction to Kvothe's further advances.
So, how does this all add up to be some "perfect"/ "idealized" woman? I mean, it doesn't sound super convincing: she's in another relationship and has a fear of commitment despite obvious attraction to the male protagonist. But this near-attainability is what makes it so attractive. There's an infinite appeal to something you can "almost" have [and that inherently wants you to have it]. There's also infinite tension in a relationship that is teetering on the border of perfect and nonexistent. These are all beautiful, charming women who are wholly compatible with the male protagonist but who resort to more shallow relationships with other men. But they are also personal, insecure individuals who struggle with feeling any sort of happiness or fulfillment in life. Due to something between a personal quality and tragic convention, these women are never going to lastingly be with the male protagonist. And Rick shows us that resolution comes with letting go. And isn't resolution so much better than infinite tension, no matter how tragic it is?