I'm sure there are plenty of people that disagree with RAH's explanation. To a certain degree, I don't agree with it. However, that's his stated logic whether we like it or not.Vehemently disagree. Either all films are art, or they aren't. One person's trash is another person's treasure. I already alluded this by saying that I prefer Aliens to My Fair Lady. My Fair Lady is arguably as much popcorn entertainment as Aliens. It was made in a time where Hollywood competed with TV with what could be called gimmicks with the roadshow-style of filmmaking. It was also the second highest grossing film of 1964. Popular entertainment. With time much of what is old gets more of a "highbrow" status, but what about My Fair Lady is highbrow? It's pretty light viewing and fairly simple. It is a film like Aliens for people with different sensibilities.
What category does Alien fall into? A haunted-house style horror but with obvious commentary on capitalism. That is more than My Fair Lady can say in my view.
As for Titanic, it is very well made, but also half of it is practically an action movie. The other half is a cheesy, badly written, romance and its portrayal of people is so one dimensional so that it can have broad, international appeal. What makes it any different from Avatar? The approach to following history is largely about aesthetics and, besides maybe how the collision happened and the way in which it sunk, is mostly fictional, especially since it focuses on fictional characters.