I think she isn't. But its because the media has always been against her. She's one of the very few in the bussiness that is genuine and a lot of people hate woman like that, she's not kissing everyone's ass and that pisses many of her fellow artists which is why they always trash her. I would argue that Christina's peak(1998-2002) is bigger than anything Beyonce has ever done. I love Beyonce but I think despite her amazing success she's always been very local, the GP probably doesn't even know her in South America
whereas Christina gets her music played all the time(even some of her flops).
I think everyone is so afraid of Xtina's power that they always try to knock her down because if she rises say goodbye to your faves.
In an ironic way the fact that Britney is an icon also puts Christina in the same status because everytime people talk about Britney(her TV specials and documentaries) they always mention Christina