My first exposure to Greta Garbo's work was, like so many Americans of my generation, through the movie Annie. I'm sure you've seen it--remember the scene where Daddy Warbucks bought out the movie theatre and they saw the Rockettes and everything? Well, after all that, they saw the movie Camille, featuring Greta Garbo. I liked the melodrama of the scene and took to swooning and saying "It's growing dark."
I didn't think about it much more until I was a freshman in college. I took a film class, and one of the films we studied was Mamoulian's Queen Christina. It remains one of my favorite Greta Garbo films, not only because of her talent, beauty, and grace, but because of the fascinating subject matter. It's a fictionalized account of a real situation: a young queen of Sweden's struggles with her role in the world.
Frankly, I thought the romantic subplot felt tacked on, but overall, it's an excellent film. Queen Christina sparked my interest in Greta Garbo, especially after I learned more about her personal history and role in the filmmaking industry of her time. I haven't seen all her films; some of them are very difficult to find. My favorites are Grand Hotel and Queen Christina; Camille actually ended up being one of my least favorites. I think Greta's character is a wussy in that one.
Mostly I admire the way she challenged the norms of women in film during her time. Directors often found her difficult to work with, since she tended to ignore direction and just did what she wanted. Luckily for the directors, that resulted some fantastic performances.