My favorite movies are not original :
Brazil, by Gilliam (basically anything by Gilliam)
Anything by Leone. The good the bad and the ugly, once upon a time in the west, and maybe above all once upon a time in america... Okay all the others too. You may cheat a bit and include Tonino Valerii's My name is nobody in it, as Leone participated enough in it, and yes, it is that good.
Dance of the Vampires by Polanski (basically anything by Polanski). It's a parody of vampire films yet, because of that, capture the essence and poetry of vampire mythology really perfectly, and manages to have a real suspense and be real creepy at times. Unlike comedic horror movies, that one doesn't alternate goofy sequences and scares, but more clevery mixes them in a continuous self-aware tongue-in-cheek genuine suspense. I adore that film. If you prefer humourless Polanski, watch The Tenant, adapted from a Roland Topor story. Surreal abstract horror that will steal your sleep for months.
Let's go for underdogs, let's promote less known jewels :
Fish Story, a magnificently clever japanese story about a meteor about to destroy earth and, in the deserted town, three people discussing in a music shop about a rock song that may or may not save the planet. It's a movie made of flash-backs, narrations, disjointed bits of biography, that only make sense and get articulated together near the end. It is a marvellous movie about humans. And it is hilarious, and each bit seems to belong to a different genre, and, well, it must be watched.
The Eclipse, by Conor McPherson. It's the best movie about ghosts (and hardly features any). And by ghosts, I mean the presence of the dead in our everyday life. The story is a simple tale of a literrary congress taking place in ireland, and a potential romantic relation developping there. But it's mostly the story of how to cope with death and mourning, and it's impressively subtle and delicate.
Also, I for one loved Vincento Natali's Cube. Take it as a standalone symbolic story, some sort of allegory, a simple little fairy tale.
The Beast of War is an awesome, gorgeous movie about a russian tank isolated in the Afghan campaign. Fantastic music, landscape, sense of isolation, and double perspective.
Das Boot is the best (or the only good ?) submarine movie. But okay, it's famous enough not to require much promotion.
Agora is a fantastic movie about religious fundamentalism. Cleverly set in a christian context to avoid essentializing association between fundamentalism and islam, yet it describes mecanisms similar to those that "Yasmina Khadra" denounces in his/her novels. It is a universal issue.
Bob Roberts is a splendid little fake documentary about the rise of a populist politician, through a team supposedly following his political campaign. This movie stays in mind.
Blood Simple is a Coen movie, and should be worshipped as such. It's a very moving little thriller about human miscommunication.
and of course, it may be easy to overlook Galaxy Quest and Without a Clue, but they are the sort of comedies where absolutely every line, scene, or split of second, is totally epic and makes, by its own, the whole movie worth watching.