I had to vote for Rowling, for a couple of reasons.
1) Every other one of the authors I've read has given me ideas. Maybe their books weren't the best on the planet, but they at least kept me (mostly) intrigued. Sure, every series has its ups and downs (Goodkind and Jordan both kinda seemed to get lost in the miasma of plot they had, for example), but Rowling... I find it hard to call that literature. Flat characters against a drab environment with very little development at all. There was nothing there to "borrow" for my own writing at all, or even give me pointers into how to write better. And no, I don't consider looking at her writing and knowing what not to do as all that valuable.
2) I've never put down a book other than hers in my entire reading existence. I even read all of Goodkind's series, even though there were parts where it got a little tough. Unless a novel is really good, I just consider it a light read, look for things I can twist and use in my own writing, and move on. Rowling, on the other hand, got way too boring. I knew what was going to happen throughout each book, and finally just gave up. It's sad, really, that so many people cut their teeth on that drivel.
That said, holy Toledo, people seem to hate Twilight! I'm glad I haven't even bothered to pick it up. And I totally agree with everyone's impression of Eragon. Completely unoriginal. Even I have more sense than to rip off Star Wars, Pern, and Tolkien and shove it all into a book without changing much of anything. I probably would have voted for Paolini if he was an option.
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