Of course there's a lot of room for improvement in Vanessa's music but she definitely is innovative, there are not many pop musicians that use classical piano melodies on their songs and that's what makes her unique in the pop scene.
I do like Norah Jones and Alicia Keys but I still like Vanessa better.
Finally, I think is unfair to still put Christina Aguilera in the same place as Jessica Simpson, Britney Spears and all the other ones, ok they all started as the same thing but Christina has innovated and evolved in every album, her new album sounds nothing like the hip-hop oriented pop music that we are so used to hear now, and if you listen to her songs you will see that many of them are about self-acceptation and self-esteem and that's a good thing, not to mention her vocal skills.