When it comes to the mainstream movies I would say without a doubt in my mind that watching "The Dark Knight" for the first time was the greatest viewing experience I had. And it doesnt get any worse with subsequent viewing.

But I am a zealot of Japanese and Korean cinema. "Battle Royale" is my singular most satisfying viewing experience I have had the pleasure of having seen. And also ahead of "The Dark Knight"(in my personal estimation) are "Memories of Murder", "Crows Zero", "Zatoichi", "Oldboy" and "Lady Vengeance".

I would have no problem in being stubborn as rating all the above as "Masterpieces" in their own right and they are all movies which never get tedious after repeated viewing.