I’ll go with:
My Man Godfrey
Maltese Falcon
Strangers on a Train
Citizen Kane
(I know a bunch people already mentioned) The Godfather
My wife would add:
The Scarlet Pimpernel (Leslie Howard)
The 12 year old version of me could see:
Logan’s Run
Mel Brooks’ Silent Movie over and over
If we can count TV movies:
I’ll add “Bleak House” (BBC version)
and my wife would like
“Pride and Prejudice” (also BBC. I proved my love by watching all six discs. Bleak House is just as long, but she liked that too.)