Since this has been a cold thread for a bit I thought I'd add a wrinkle for the heck of it...my favorite movie for each year beginning with the oldest movie/year I know. Sometimes more if necessary.
1900s 31-50
31: City Lights
32: The Champ
33: King Kong
34: It Happened One Night/Thin Man
35: Mutiny on the Bounty
36: A Tale of Two Cities
37: Lost Horizon
38: Boys Town
39: Mr. Smith Goes to Washington, Beau Geste, Gone with the Wind, Stage Coach, Wuthering Heights, Of Mice and Men, The Wizard of Oz, Dark Victory
40: Grapes of Wrath, Rebecca, The Great Dictator, Philadelphia Story
41: Malteze Falcon, Sgt. York, Suspicion
42: Random Harvest
43: Casablanca, The Ox-Bow Incident
44: Gaslight
45: Spellbound
46: It's a Wonderful Life
47: The Bishop's Wife, Gentlemen's Agreement, Miracle on 34th Street
48: The Treasure of the Sierra Madre, Red River
49: All the King's Men, Battleground
50: Sunset Boulevard
1900s 31-50
31: City Lights
32: The Champ
33: King Kong
34: It Happened One Night/Thin Man
35: Mutiny on the Bounty
36: A Tale of Two Cities
37: Lost Horizon
38: Boys Town
39: Mr. Smith Goes to Washington, Beau Geste, Gone with the Wind, Stage Coach, Wuthering Heights, Of Mice and Men, The Wizard of Oz, Dark Victory
40: Grapes of Wrath, Rebecca, The Great Dictator, Philadelphia Story
41: Malteze Falcon, Sgt. York, Suspicion
42: Random Harvest
43: Casablanca, The Ox-Bow Incident
44: Gaslight
45: Spellbound
46: It's a Wonderful Life
47: The Bishop's Wife, Gentlemen's Agreement, Miracle on 34th Street
48: The Treasure of the Sierra Madre, Red River
49: All the King's Men, Battleground
50: Sunset Boulevard