First of all, the vast majority of people can't even come close to replicate this "technological experience" of movie theater. The huge screen as well as the audio system absolutely do change how you experience a film, be it Avatar or 2001 or Metropolis (the last two of which I've only recently seen for the first time on the big screen, and even though I have a pretty huge TV, this was an entirely different experience).
But aside from the technology involved, a movie theater is a completely different environment than your living room, it is designed to keep you entirely focused. I find I am much more immersed in a movie when I see it in the cinema. Also, some movies are just made to be watched as part of a larger audience (e.g. I can't imagine I'd find Borat even remotely as funny as I did when I watched it in a small theater packed with a cheering crowd).
On a somewhat more esoteric note, I seem to remember a study that showed rear-projection (like on a TV) had a different impact on the brain than front-projection (like on a movie screen). I can't find anything about this now and it might've been complete bogus, but maybe someone else knows something about this...