Outside of comic book fans, of which there are plenty, I would strongly argue that Gaiman has almost zero name recognition. His fans are devout and buy his books immediately, but they haven't had much staying power on the list. That, and he's only had three books to ever make the list (American Gods, Sandman Endless Nights, and Anansi Boys), with Anansi Boys the only one to ever reach #1. There is a reason why they are not using his name in any promo for the film, it's because he isn't considered a positive commodity in Hollywood. His fans will come, maybe (Mirrormask made less than $1 million and the majority of that was here in Minneapolis), but he certainly isn't viewed as any sort of long-term drawing card. That's what DeNiro, Pfeiffer, et al are for. That being said, with Beowulf coming out this fall, and Coraline later next year, Gaiman is poised to be a breakout star. But for the moment, he has little to no mass appeal in terms as a script writer/producer. And being that I am a long-time ardent fan myself, having been to I don't know how many signings and attending even more of his readings, I'm quite content in realizing his appeal isn't to a very broad audience. He even makes light of it himself, as he tells the tale of his Mall of America signing disaster with relish almost any chance he gets. But go see the movie with thousands of friends and I will happily admit I am completely wrong.