District 9

You should definitely see District 9, if you haven't already. It's even more original than Cloverfield, plus the camerawork won't make you queasy. You can parse it out on about five different levels, but I don't want to give anything away, because I only knew a little about it from the trailer and io9 now I wish I hadn't even known that.

It did well at the box office over the weekend (#1), but unfortunately I suspect its foreign flavor will keep it from being ranked among the all-time best SF movies, at least in America. For that it would have had to be set in Los Angeles (which would have totally ruined it, or course, if you're a real sci-fi fan).

See it.