There's no way to point to one. I can't do it.
Inherit the Wind
Goodfellas
L.A. Confidential
Star Wars
Note, these are among my favorites, obviously, but a lot of my faves are fantastic movies but not Great Cinema (ie, Spinal Tap, all the Christopher Guest movies, Princess Bride.
12 Angry Men was a good choice. Citizen Kane as well, though I find Touch of Evil more compelling.