I've only seem some of these... I'll have to check out the others. Here are my thoughts.
Children of Men: My favorite movies of all time, thus far. This film is proof that you don't need quick cuts, shaky cameras, and fancy special effects to make things exciting. And it has my favorite character death scene in all cinematic history.
Dark City: Fun movie, nice twist, awesome themes, but I hated the way it ended. I think it could have been done much better.
Pi: I wasn't quite sure what I thought about this movie after I saw it, but it certainly was enjoyable.
Primer: I love the way that this movie attempts to create a new set of mind-bending time travel laws that aren't found in any other movie, doesn't talk down to the audience, and allows there to be unsolved mysteries left dangling at the end that are literally impossible for anyone to figure out.
The Matrix: Yeah, how could you
not include this in the list?
Minority Report: Didn't really like it that much. Then I heard a theory that everything that happened after Tom Cruise's character was put into stasis is a hallucination. Now I love it.
Gattaca: I was extremely impressed with this movie. I thought it would be dull, going into it, but it managed to keep me on the edge of my seat the entire time, along with being thought-provoking and part of a well-crafted universe.
Donnie Darko: Maybe it's because I watched it with friends late at night the evening after I flew back to California from England... but I didn't understand it. At all.