So, for the first 11 Academy Awards for Best Picture, I count three that I'm pretty confident were decent choices (All's Quiet on the Western Front, It Happened One Night and Gone with the Wind [even though I would have preferred Wizard of Oz.])
So as for the next five years:
1940 - The winner was Rebecca. The other nominees were All This and Heaven Too, Foreign Correspondent, The Grapes of Wrath, The Great Dictator, Kitty Foyle, The Letter, The Long Voyage Home, Our Town and The Philadelphia Story. Several of these choices would have been good. Grapes, Dictator and Philadelphia would all have been worthy in my book. But I'm okay with Rebecca as Best Picture. The greatest injustice this year was Alfred Hitchcock not winning Best Director for Rebecca (he directed Best Picture nominee Foreign Correspondent as well.)
1941 - The winner was How Green Was My Valley. One of the big mistakes by the Academy. Because among the nominees, along with Blossoms in the Dust, Here Comes Mr. Jordan, Hold Back the Dawn, The Little Foxes, The Maltese Falcon, One Foot in Heaven, Sergeant York, and Suspicion was Citizen Kane, which often comes out on top of polls as the greatest film ever made. (And if not for Kane, Falcon is better than Valley as well.)
1942 - The winner was Mrs. Miniver. The nominees were The 49th Parallel, King's Row, The Magnificent Ambersons, The Pied Piper, The Pride of the Yankees, Random Harvest, The Talk of the Town, Wake Island and Yankee Doodle Dandy. I haven't seen all of the nominees, but I've seen most, and I'm happy with Miniver as the winner. Bonus, Dr. Joseph Goebbels, head of Nazi Germany's Ministry of Public Enlightenment and Propaganda was extremely jealous of the film and believed it made a huge difference in the Allied war effort.
1943 - Casablanca was the winner. I don't need to list the nominees. Since Citizen Kane wasn't made this year, what could be better than Casablanca?
1944 - Going My Way was the winner. The Academy this year switched to the more manageable number of five nominees. The other four nominees were Double Indemnity, Gaslight, Since You Went Away, and Wilson. Since You Went Away and Wilson are both pretty bad. Gaslight and the winner Going My Way are pretty decent. But Billy Wilder's Double Indemnity is a masterpiece.
So that makes three good choices out of five for a running total of 6 out of 16 Best Picture choices that I'm pretty sure were decent.