As to those 3D movies which are currently shown in theaters, that level of tech requires the wearing of special glasses to make the 3D image viewable. FWIW, these glasses have a invisible shutter to them that blinks at a certain rate that the brain 'translates' to a coherent image. This blink rate is 'almost' invisible and imperceivable.
What the unconscious brain perceives and translates is a slight time phase or a slight delay between left and right eye. (think back to the yesteryear when there were stereoscopic slide viewers from the late 40s - 60s.).
This slight time difference is what the brain resolves as a spatial (depth) difference or a 3D image. Without these glasses in theaters (with the current 3D movies), you see a non-3D image. At home on TVs the current TV tech renders to the viewer as a bit different and less realistically but still definitely a 3D image.
FWIW, I prefer watching movies such as Avatar
in 3D (as opposed to home viewing). That sort of movie excells in theater 3D movie technology. If technology fascinates you, you should at least ONCE see a movie of your taste choice in a theater that shows 3D.
Of course, they often couple these blockbuster releases of 3D Movies at OMNI-equipped theaters in major cities like NYC Wash DC, Chicago, Toronto, LA, SF, Boston, Tampa, etc. You have to be purist, or pretty jaded or techno-phobic to dislike this.