I agree. Joan was glamourous in Humoresque, as well as stylish. A combination of makeup, costumes, lighting and, of course, that great hair. She had always been a physically striking woman but the years had somehow matured her features to make her more interesting, less hard, by 1946 when she made this film. I never thought she looked more attractive than in Humoresque, even with those little reading glasses on.
I agree that Joan is at her best in Humoresque -- both in terms of her appearance and her performance -- but she's helped by great co-stars, music, and writing. It's one of the few of her later films where the male lead is as strong as she is, and Oscar Levant steals every scene he's in. The score is fabulous, and if you can get a CD called Humoresque by violinist Nadia Sonenberg, in whch she plays many of the selections played by Isaac Stern, you're in for a treat.
I think Humoresque and Mildred Pierce are my two favorites of Crawford's 40s era, and the latter is also blessed with a great cast. and wriitng. Eve Arden is kind of the female counterpart of Oscar Levant and has some great lines, and I'm sort of rooting for Mildred to end up with Jack Carson of all people.
Of Crawford's earlier work, I'd say Grand Hotel and Rain are her best. Her performance in Grand Hotel is very natural and honest, while I find Garbo rather stilted and dated.
That being said, I still see Crawford as more of a "star" while I view Davis as being more of a real actress. When people talk about Crawford's beauty, I think the word "glamour" is more applicable, as glamuor is about a beauty that is created or manufactured. Crawford had a gift for projecting glamur, but I wouldn't say she was one of the most beautiful woman on screen in the 30s or 40s. Ingrid Bergman, for instance, was someone who I feel was one of the greatest natural beauties on screen, without any need for glamour.