I rarely see movies in the theater for a couple of reasons: it's gotten really expensive, I have a small child, and too many people act like they're at home instead of in a public place and ruin my movie-going experience. If you have your own theater at home, you can make as much noise as you want, the concessions are much cheaper, and no previews. While the initial installation can be pricey, you never have to leave the comfort of your home. Many of us have far bigger TVs than our parents could've dreamed of as kids, but a true home theater experience means a room devoted specifically to TV and movie viewing.
This often means a darkened, soundproofed room set up with big, comfy sofas or recliners. Drink holders and trays make it easy to enjoy your favorite beverage and snacks. While you're at it, a mini-kitchen with a fridge, microwave or even a popcorn machine means not having to bring anything from the main kitchen. Of course the TV is the big star here. What kind you get depends largely on your preference, but these days you'll probably choose among a high-definition LCD, plasma, LED or DLP (rear projection) television. Some would argue that unless it's projection and at least 70 inches, it's not really a "home theater", but that's up to you. What about a 3D TV? You'd just need enough glasses for all of your guests.
Wall-mounting your TV or a screen that folds or lowers from the ceiling would be ideal. You'll also want an HD Blu-ray player, of course. And what would a home theater experience be without premium sound? Some stores sell home theater systems, which include multiple speakers and a subwoofer for a surround sound experience. Thankfully, you can find professionals to install and integrate all of your electronics.