Hollywood is betting on 3D movies the way it was betting on anti-war movies a few years back — and with similarly disappointing results. Let’s admit right up front that Hollywood gimmicks can be fun and as James Cameron proved, quite profitable. But over the long haul, movies come down to good stories, well told — first and last and everything in between.

So what’s the deal with 3D? Let me admit right up front that I just don’t get it — or didn’t, until very recently.

I’ve only seen three 3D flicks so far. The first one, 2006′s Superman Returns, was awful. The movie itself was more or less OK, as a completely unnecessary sequel to 1981′s Superman II. But the 3D was just bad. Almost the entire movie was in plain old 2D, so you had to stay ready for the cue to put on your glasses for the big action sequences. Then the 3D itself was so poorly implemented that you could hardly tell what was going on. The Space Shuttle sequence looked better on our 50-inch Mitsubishi than it did on an IMAX screen. Yikes.

Whatever has been done to the 3D sauce since then, it’s much improved.

This summer I’ve taken my son to two movies, both requiring special glasses. Toy Story 3 was a worthy successor to the first two movies, and yet another Instant Classic for the folks at Pixar. I don’t know how they do it, summer after summer. But the 3D? It neither added nor detracted from the essential quality (and our enjoyment) of the movie. The other one was How to Train Your Dragon. And let me tell you, not only was that a perfect summer kids’ movie, but it was made better by 3D.

Why the difference? Both shows were aimed squarely at the juice-box set. Both were computer animated. Both had quality scripts (even if Pixar’s was at least one notch better than Dreamworks’). Both were lovingly rendered. Both were fantasies. So why was one made better with an extra layer of digital trickery, while the other wasn’t?

I have to guess here, but I think it comes down to scale.

The Toy Story characters inhabit a world we know — a world small enough to fit in a child’s room. And the characters themselves can almost fit in your pocket. Does it really matter if a ten-inch action figure pops out of the screen? No, not really. Just be thankful the effect was done well enough not to ruin the movie.

But flying, fire-breathing dragons, soaring above rocky fjords and a half-frozen ocean?

Bring on the 3D, baby, and make it pop.

Which, aside from the novelty of someone finally mastering 3D trickery, is probably a big reason Avatar did such big business. People weren’t returning again and again, at premium ticket prices, for James Cameron’s snappy dialogue.

So, do you get it, Hollywood? In the right circumstances, 3D can put more bottoms in theater seats.

But mostly we’d just like a good story, well told.

UPDATE: For the record, A.B., I’m still not totally comfortable with pr0n at DVD definition.