Well, this kind of list is always partial, IMO. Even if the best directors and movie experts of the world had done it, it still would be partial.
Movies are particular. You like it, someone else doesn't. Of course, there are movies most people like, but it's almost impossible to say "this is THE best movie".
It's AFI's opinion, may not be the Academy' opinion. May not be your opinion. You shouldn't take it as the complete and unchanging true, but as a point of view. At least that's what I always try to do.

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