There are many differences. So, I will have to be selective. Here are three differences.
First, the most important difference is context. When you are watching television presumably at home, you can do whatever you want. You can stop the movie, fast forward it and pretty much anything you want. Hence, it is much less formal. When you are at a theater, it is a public place. For this reason, you need to act according to behaviors that are socially acceptable. This can make the movie much more enjoyable, because there are social constraints for you to actually watch the movie without distractions. This attention goes a long way in enjoying the movie.
Second, you pay for the movie, whereas television is free. For this reason, you are more apt to only watch movies at a theater that you like. Also you are monetarily invested, which can add to the enjoyment.
Finally, the scale and quality of a theater are much better than anything at home.