Well, she's always made me sick. But, your question is interesting. I think she's regarded as an intellectual because she uses complex grammatical constructions and college words. I think she's famous because she positioned herself as the typical romantic/suffering/victimized/doubt-torn intellectual that western civ loves. As Stephen Greenblatt used to put it in conclusion to many of his lectures "There is hope, but not for us.".....without ever actually defining who "us" is. But I suspect that "us" is a flavor of angst-ridden institutionally-nested intellectual that both Sontag and Greenblatt exemplify.
Joanna Bujes