The Academy Award for Best Picture is the highest honor the film industry can bestow on a movie, but it doesn't necessarily bestow greatness. Only the passage of time can do that, which is what makes a perusal of history's Oscar winners so remarkable. The academy almost always gets it right.
The exceptions, however, are glaring. Voters have gone with distressingly safe choices too many times through the years, and even when they've grown daring the results haven't always stood the test of time, or have been canceled out (In the Heat of the Night's win in 1967 was an astute reading of where America stood on the issue of race at the time; Driving Miss Daisy, in 1989, not so much).
Any list of the most controversial Academy Award winners for Best Picture is necessarily subjective, but the consensus on Oscar's biggest "huh?" moments is nonetheless solid. What were they thinking, indeed?