The comparison of 3D TV and VR is indeed interesting. . .but complicated. (Or maybe interesting *because* it's complicated.)
The biggest factor in 3D TV's decline seems to be lack of content -- very few movies were actually shot in 3D, but instead we were given a lot of cheap conversions and no easy way to identify them as such before watching. Hollywood really dropped the ball on this. Also. . . Movies have been pretty well developed as an art form in 2D for many decades, and this seems a bit like an effort to fix what wasn't broken. Furthermore, a 2D motion picture, especially when there's any sort of camera movement (panning, especially), already provides a lot of unconscious depth information.
BTW, 3D TVs are still selling. Most of the higher-spec TVs on the market still include the 3D feature. I find it useful for viewing stereo photos taken with my Fujifilm REAL 3D W3 camera. Stereo photography has a history of huge, mass-market success -- now mostly forgotten. In the 1800s, before automobiles and consumer-ready box cameras caught on, professional photographers went around the country and around the world shooting 3D images and printing them on Holmes stereo cards. Peddlers would then go house-to-house selling bundles of stereo cards, and that was how you got to see the world. A virtual vacation!
The Fuji isn't a great camera in 2D terms, but the stereo images really are striking and beautiful when shown on my TV set. And stereo photos are especially well suited to some kinds of subject matter -- like plants and trees, which often seem to turn into a camouflage-like jumble in mere 2D images.
Getting back to VR. . . I am very skeptical of watching movies in VR. It doesn't make sense to me. You can't move around freely. You can't interact with your surroundings. It's not "VR" in a conventional sense of the term. It's just. . . 3D TV, with poor resolution, plus head tracking. And the head tracking seems like more of a problem than a benefit, since you may be looking the wrong direction when the action starts. I won't be surprised if VR cinema is a flop, but so what? That's not what VR was really about anyhow.
VR is best, and makes more sense, when putting you into a dynamic simulation. Many games are dynamic simulations, so that's a natural fit. And the game industry is huge. It's bigger than the music industry, and it's bigger than the movie industry. All this hand-wringing in the blogosphere about the need for VR to "reach beyond games to find a mainstream audience" is bunk. Games are mainstream.