Like The Night of the Shooting Stars : this is a pretty well-respected movie among film buffs, but, well, I think it deserves a lot more. I mean, there are some movies that don't really work for me that I am willing to accept are masterpieces - Battleship Potemkin or 2001: A Space Odyssey. In return, all I ask is that everyone else accept The Night of the Shooting Stars as a masterpiece - even if it doesn't bowl you over.
There are so many things I love about this movie: both in terms of (a) "what it's about" and (b) "how it's about that". An example of (a): there are few other war movies that manage to so fully and generously humanize everyone involved in the conflict. Maybe the most moving, wrenching, horrible scene in the movie is for the death of a character that a less generous (and less audacious) movie would have us cheering for (yes, I'm looking at you Pan's Labyrinth). As for (b): I can't help but thinking of this movie as a "movie movie" - one that makes use of all the various styles and idioms of European narrative film throughout the century - expressionism, poetic realism, neo-realism, etc. What's amazing, though, is how seamless the whole picture is, despite this variety.
Another great movie that has fallen through the cracks: Where the Heart Is . My theory is that this is one of those movies that scares off its ideal audience because of its surface appearance. Specifically: it looks kind of like a late-80s, John Hughes-ish family comedy - wacky parents, wacky kids, wacky situation. And it has a synth-driven musical score! But underneath, it's more like a sophisticated European comedy. Oh, yeah, also - it's one of the few contemporary movies/books/plays/etc. that tries to be Shakespearean that, IMO, actually feels Shakespearean.
Now - I would like to point out that I also try not to confuse "underrated movie" with "cult movie". For example, I think The Red Circle is just fantastic, but it's a meandering, existential, not-very-thrilling crime thriller/heist movie. I'm not quite sure that it is even meant to appeal to a general audience. But The Night of the Shooting Stars and Where the Heart Is are both really "general interest" kinds of movies.
So, I'll add on one more for now: Philip Kaufman's version of Invasion of the Body Snatchers . I was just watching this again and was struck by how right all the little details seem (especially all the background weirdness). There are a lot of "small group against alien/zombie/etc. invasion movies" but the strength of this one is that it is so believable on a realistic level. I didn't find myself making excuses for it ("Oh, well - they have to do that because it's a movie"), in the way I find myself making excuses for some of the inconsistencies in, say , 28 Days Later.
It's a masterpiece of suspense and paranoia: the kind of sci-fi movie Jean Renoir might have made.