I think a fairer comparison is series/books vs anime/manga (or perhaps movies/comics), of which admittedly there are far fewer examples. You have to take into account that a movie has to tell the story of an entire book in ~2 hours, whereas an anime has at least, let's say, 5-6 hours (12 episodes times ~25 minutes). As such, a movie based on a book is almost assuredly going to leave things out. In the end though, if it can still grab your attention and hold it for all of those 2 hours, it might even be better value for your time than an anime which might sometimes be forced to add filler episodes because they've used up all of the currently available source material (another issue movies based on books don't have, since a book, even if it's a book in a series, is almost always going to be, a finished story, whereas manga-based anime are often still ongoing). In the end, I think it's hard to compare most of the time. They're different media, and as such, different rules apply.
