Well X... you had me convinced until this:
"But to say that movies are supposed to be entertaining and nothing else is equivalent to saying that music is only supposed to have catchy tunes and infectious beats."
-Xantar-
(had to try the CamFu Quoting again

)
I think that these are completly different things. Some music doesn't need words to express itself.
What is a Movie, Music, or even Video games? Entertainment. Music, Movies, and Games don't have to make you think as long as they are Entertaining. There are no levels to this.
If music's cacthy tunes and infectious beats are entertaining, the music served it's purpose,
Entertainment.
A movie is the same, it can have no story line, and be utterly pointless but still be
entertaining. You relize how many porn flicks sell? Or even cartoon movies? It's not about having a "point" people just wacth it to be
entertained.
Video games fall into this too. The game voted best game of all time by most sources, Tetris, is one of the most shallow games of all time. But what it does is
entertain.
I'm not going to argue with everything else you said, because it's your opinion. But this last line makes it sound like you think entertainment isn't supposed to be the main goal of movies. Even educational movies are entertaining to people who want to learn somthing from them.
Maybe you should change your wording if I misunderstood you
