First of all, when I saw this Wednesday night at the Arclight, they didn't attach the Indiana Jones trailer to it - WTF? (Of course, I've downloaded it a few times already - it's sloppy but I'm excited.)
Childrens' movies are funny things. We tend to overvalue the movies that we grew up with and look down on those of a later generation, which of course isn't fair, but what can you do? The movies we saw as kids are, for most people, the way we learned to watch movies in the first place, our original encounters with chills and thrills, and it's hard to detach oneself from such primal experiences.
Anyway, as specifically regards The Spiderwick Chronicles, I gave it a shot because the trailers made it look like something potentially special: a kid's world expanded by the revelation that there's a secret world just outside the reach of the everyday, accessible to those in the know (in other words, I wanted to see if it would be this generation's The Neverending Story). The film involves Jared Grace (Freddie Highmore, from Finding Neverland and Charlie and the Chocolate Factory), who moves with his family to a big creaky old house in the aftermath of his parents' divorce, and quickly escapes into a world of ogres and fairies and whatnot.
The primary problem with the movie is that even though it's loaded with spectacle in the form of the various CGI trolls and griffins, it's a little short in the wonder department, as the screenplay is so rushed and full of action that little time is left over for the discovery of the unseen world, for the development of suspense and uncanniness - the CGI drowns out the basic, more subtle emotions. The secondary problem is that the underlying subtext of the movie - that the fantasy world allows troubled Jared Grace to learn to cope with his parents' divorce, a la Elliot's situation in E.T. The movie obligingly gives Jared a cathartic substitution (SPOILERS) by having the movie's Big Bad guy turn into Jared's philandering father for one scene, just long enough for Jared to stab him in the chest (!), after which he goes back to being a CGI troll. Direct, yet clumsy filmmaking, and it lacks a proper emotional throughline or perspective.
So even though the movie is an entertaining ride, it's a mixed bag because the filmmakers have chosen to prioritize CGI action over simple storytelling and emotional meaning. It's the same thing that tainted last year's otherwise-excellent Bridge to Terabithia and threatens to tilt each year's Harry Potter movie into nonsense, except for Alfonso Cuaron's episode.
A few other points: I do give the movie credit for being really scary and intense in places, as a good kids' movie should be. Freddie Highmore actually plays twin brothers in this movie, doubled by digital mattes, which is distracting - I can see why they did it, but it still means that the poor actor's performances are frequently disjointed. Also the music is by serial self-plagiarist James Horner, who this time rips off his score for A Beautiful Mind.