Carla Fracci and Eric Bruhn were memorable. She has the true Romantic style and was memorably ethereal. Ferri has some of same qualities.
Although she was not considered a great Giselle, I have wonderful memories of Cynthia Gregory's debut in Milwaukee when I was a teenager. She was so fresh and innocent, a lovely debut.
I also loved Marianna Tcherkassky's performance.
There is a wonderful video called "Portrait of Giselle." Narrated by Anton Dolin, a famous Albrecht in his time, and it shows Olga Spessitva (sp?)in the mad scene. The most extraordinary one, I've ever seen. The tape ends with Dolin coaching Patricia McBride and Helgi Tomasson. Well worth seeing if you can find it.