Thing about 3D films is that directors are finally learning how to make them.

It sounds easy (just replace the normal camera with a 3D one), but it isn't.  For instance, a standard camera technique is to focus (literally) on what you want the audience to look at.  Trying that in 3D is one of the things that cause viewer headaches because their eyes will likely be roaming over the screen, including areas that are out of focus at any given minute, which causes eyestrain because the visual system is trying to compensate for something that it can't compensate for.

The better directors are figuring out you can't do that.  You might have to film a scene with an infinite focus range, just like reality is.