I said that Alien is one of the more overrated movies out there. Because despite it being an old fashioned monster movie that was made using superior art and techniques it doesn't really have that much significance above that or enough depth to hold up to scrutiny. If you accept that it's just a simple monster/slasher and that any message or plot is mostly irrelevant as long as it isn't confusing, and that's what you want, then I don't have a problem.
I think everyone accepts that it's a simple monster movie. That doesn't mean it's overrated. In fact simplicity can be a very admirable trait in a film that is so exactingly crafted as Alien (or JAWS for that matter). It's not just the visuals that the film is celebrated, but the Freudian psycho-sexual nightmare the alien induces, the grounded performances, the taught screenplay, the perfect pacing with a measured build up to the explosive final act, the sense of mystery and lack of exposition, coherent characters.
Just because it doesn't engage in as complex themes as something like, say Apocalypse Now, does not mean it isn't as great a film as any of the other classics. Perfect execution in film no matter the subject is a rare and incredible thing, and the film's legacy and impact speaks for itself. It doesn't need monologues or complex characters in order to engage it's viewers and touch upon deep seated fears that are all the more believable due to the grounded setting of the movie.
And it doesn't have the depth to hold up under scrutiny? What exactly falls apart under scrutiny? I would wager that nothing of any import falls apart because the movie is so tightly constructed and well thought out from themes to character arcs. Compare that to Prometheus in which even a cursory evaluation of it and the film falls short in myriad ways.
Ultimately though, to suggest that a movie is overrated because it's "only" a monster movie is a rather shortsighted evaluation of the medium.
