Gary, you're being far too polite to the offenders. I've found that a quite effective way to alter the behavior of idiots in a movie theatre is to get a VERY angry look on your face, shoot an "ahem" in their direction, and when you've got their attention, tell them VERY sternly to shut the hell up and turn that frakking/gorram* cellphone off. (I don't care if they're talking on it or using it to text someone. If I'm aware of it, it's a problem.) This has always worked for me.
But I agree that there are far too many rude asshats walking the earth nowadays, and they all go to the movies. A home theatre is great, but it really is not a proper substitute for a giant movie screen and an earth-shaking audio system. I refuse to surrender to the rude and the moronic, so I will keep fighting the good fight.
* Insert proper expletive here. Yes, I do say this to complete strangers. Sure gets their attention.