I say: 1. Se7en 2. Zodiac 3. Fight Club 4. Social Network 5. Panic Room HM: The Game, and Curious Case of Benjamin Button. Overall, I think there's a gap between Se7en and the rest of his movies. Zodiac, Fight Club, and Social Network are all quality, but Se7en is several leagues above them. Panic Room is a very underrated movie. The Game is underrated too.
I think Benjamin Button is an ATG film as well. I'd say that film and Seven stand out as his two masterpieces.
Shit, I forgot Gone Girl and The Girl with The Dragon Tattoo are Fincher movies. New list: 1. Se7en 2. Zodiac 3. Fight Club 4. Gone Girl 5. The Girl with the Dragon Tattoo