You may remember that when Helen Hayes (I believe) was announcing the winner, she made a Freudian slip (most likely not a senior memory lapse), or perhaps just a snide observation, referring to the film as "Ordinary Movie."

If you factor out crass commercialism ("help the big budget film compensate for its investment") tend to prefer dubious sentimentality over unpleasant psychological insights (the staple of horror films, especially those like Se7en). I suppose a maudlin tentpole horror film (which is horrible just as a concept) would have a fair chance of getting Best Picture. (Same sort of schmaltz tends to dominate Best Foreign Film choices as well.)