3D cannot make a movie better... much in the same way that you can't polish a turd...
I find 3D displays fascinating in ther own regard, from a technical & logistical standpoint, but the adding of another dimension to play with in composition alone suggests that there is artistic potential to be exploited.
I would have to in turn ask why 3D is so offensive to people? Does it really give you a headache and hurt your eyes? I've seen Avatar in the theatre and that's basically it for my 3D film-going, but I really, really enjoyed the cinematic experience of it. I've said it before, but it's like watching Dorothy and Toto come out in color... it's just pure visual rapture.
On the flipside, oftentimes when I see a 3D picture from a stereoscope, or something like that, I'm left with the impression that, hmmm... ok, that's what it looks like in real life. *yawn* In that respect, I can relate to some 3D skepticism.
However, there are very intriguing possibilities with hyper & hypo stereo setups; where the "eyes" are placed much further or closer than our interocular distance. Imagine two cameras 50 feet apart and aimed at a distant thunderhead; the thunderhead becomes a dollop of whipped cream. Likewise, 3D microscopy, showing a virus or cell in full relief. This kind of stuff interests me.
update: a lot of these posts are just down right curmudgeonly IMO