Patrick Goldstein asks here why the Grammy nominees are so much more populist than Oscar nominees. Big selling records win Grammys; not-so-big-selling “serious” movies - critical favorites - win Oscars.
One reason might be that there is less aesthetic distance between Katy Perry and Arcade Fire than there is between “Jackass 3-D” and The Kids are Alright”. To put it crudely, smart pop music is more similar to dumb pop music than smart movies are to dumb movies.
The real question is why a discussion of Grammy nominees is exclusively confined to pop music. Of course the award will seem more “populist” if you only have pop music on your mental map and you eliminate the top shelf stuff - the jazz and classical nominees - from the discussion.