I believe when people look at Sandra Bullock they look beyond her physical attributes. Although she is very attractive I believe her personality and always coming off as humble or down to earth with her self deprecating humor raises her attractiveness.
She seems "real" and approachable.
People actually feel like they could be friends with her.
Lots of fans were upset after learning of her ex-husband cheating on her while he sat in all the award shows listening to her accept the SAG, Golden Globe, and Oscar praising him every step of the way.
In many ways she's "America's darling" compared to other actresses in Hollywood. Ever notice that the most beautiful or sexiest person in the world is always famous and an American?
There's probably some anonymous woman laying on the beach in Tahiti right now who is more beautiful than any actress.