My picks--if some of my dates are off, well, just mentally put 'em where they belong:
1940:The Thief of Bagdad
Runners Up:Rebecca, Philadelphia Story
1941:Citizen Kane
1942:Casablanca
The Magnificent Ambersons, The Palm Beach Story
1943:Shadow of a Doubt
The Seventh Victim
1944:Double Indemnity
Laura, The Miracle of Morgan's Creek, To Have and Have Not, Since You Went Away
1945:Lost Weekend
Leave Her to Heaven, Detour, , Picture of Dorian Grey
1946:Best Years of Our Lives
The Big Sleep, Great Expectations, Notorious
1947:Out of the Past
1948:Treasure of Sierra Madre
Key Largo, The Lady from Shanghai
1949:The Third Man
The Fountainhead, The Heiress