James Stewart's Oscar was undeserved
As far as I am concerned, Jimmy didn't deserve the Oscar mainly because there were better performances that year such as Laurence Olivier in Rebecca or especially Henry Fonda in The grapes of wrath. In addition, it wasn't the best performance in the film because Katharine Hepburn and Ruth Hussey(who was amazing) were far better. Don't get me wrong, I love James Stewart and he was quite good but he should have won for Mr.Smith goes to Washington or Anatomy of a murder and not for this film. However, I really liked this movie and it really deserved best adapted screenplay Oscar.
This would have been my choices in the acting categories:
Best actor- Henry Fonda-The grapes of wrath
Best actress-Joan Fontaine-Rebecca(I don't know how Ginger Rogers won)
Best supporting actor-Walter Brennan-The foreigner
Best supporting actress- It would have been difficult to choose because all were just amazing but perhaps Jane Darwell would have been my choice.