As I have not seen either AS or Boyhood up to now, it is hard for me to utter an opinion on them, but I am thinking the most worthy movies for BP are the ones that are really well made and were seen by a lot of people. Terrible but popular fanboy movies or artsy movie nobody really is interested in should not be considered.
AS got a BP nomination (it is a movie I am really intersted in seeing) and now it makes a killing at the BO, so I think it is a worthy movie. Wether it should get the award in front of the other contenders, I don't know. But if it really gets an extreme BO in the end and not win BP, than people will be annoyed by the academy, whether deserved or not doesn't matter that much, but the Oscars will suffer and get irrelevant year by year.