Three indisputable masterpieces (among many) that carry, for me, specific memories of being thrilled, memories of time and place.
Two from Kubrick (a little strange, because I'm not all that nuts about the rest): Dr. Strangelove and 2001-- Dr. S., sitting around a tv in my Sister's appartment, and 2001, in a huge old wide screen theater with my Father.
And one that hit me in a way that nothing else has, before or since. I was glad I saw it in a theater, in the afternoon, alone, because I was emotionally destroyed: Schindler's List.