Unfortunately, she wasn't a great actress. Her face was intriguing, which was important in silent films, but her exotic mystique in the public eye was more responsible for her box office success than anything else.
Others who were good in silent films and made a successful transition to 'talkies' are Joan Crawford who was hugely popular in silent classics like Our Dancing Daughters, and then of course having a legendary career in sound pictures, including Mildred Pierce, Humoresque, Strange Cargo, Possessed (two different films by that name, one with Clark Gable, and one later on--not a remake, a totally different story), The Women, and many others. Barbara Stanwyck also made some good silent films before moving on to classics such as the great film noir Double Indemnity. Gloria Swanson was perhaps the biggest silent era star alongside Greta Garbo, and Gloria went on to do one very good talking picture: Sunset Boulevard.
My favorite Greta Garbo picture is Grand Hotel. It takes advantage of her public image as a legend, but since it's an ensemble film, and she is surrounded by great talent, there is no problem of Garbo needing to carry a picture on her own. Joan Crawford is in this film with her (no scenes together, however) along with Lionel Barrymore, John Barrymore, and Wallace Beery.
I think Garbo had enough sense to realize that her star was beginning to dim as Joan Crawford's popularity soared at MGM in the 1930s, plus Irving Thalberg at MGM was giving more and more great roles to his wife, Norma Shearer, so Garbo wisely reduced her projects and then retired altogether. Then she became a living legend for the remainder of her days.
