I disagree that this film was not intellectual. I thought it explored some interesting questions. Some of life's biggest questions are, where do we come from? what are we here for? and where are we going? and I like that this film broached the subject. It didn't do it an incredibly innovative way or anything, but still, it was nice that it did.
Can you explain what you mean when you say that Alien is a thinking man's sci-fi though? How do you mean exactly?