A fantastic sci-fi. Great acting; great special effects; great balance between suspense, comedy, and drama. Also, most of the usual sci-fi cliches were expunged or reinterpreted.
The best movie I've ever seen is Citizen Kane. The Dark Knight is the best movie I've seen in a theater. While all elements of the film were highly effective, words cannot describe Heath Ledger's chilling transformation into The Joker.
The bottom line is that the plot to this movie is thoroughly unentertaining, perhaps because all the essential elements of Shyamalan are missing: No imaginitive setting, no creative puzzle to solve (the solution is provided very early into the movie), and no twist ending. I suspect disappointing reviews of his last two films lead to the "extensive rewrite" of the script that is noted on Wikipedia. Mr. Shyamalan, you're such an excellent director, as even this film was expertly directed, but I implore you to allow someone else to do the writing.