I've never heard of Eragon, but even if it's a a great book I'd have to agree with this:
Quote:
Would a dragon be enough for Eragon if he and Harry shared release dates? Probably not.
It may be a great book, but Harry Potter was already very popular and people had been anticipating OotP for a while.
It doesn't have to do with which book is better or not, it simply has to do with how well-known the books are and popularity.