Most critics (who themselves are incredibly pretentious) will tell you pretentious is a bad thing.
But in reality, I find that most music is pretentious in some way or another, and that artists who are not pretentious or at least try not to be tend to suck ass.
I don't think Jim Morrison was any more pretentious than Lou Reed or Leonard Cohen, or that ELP are any more pretentious than Pavement. I think that overall, any music that tries to be artistic in anyway is automatically pretentious, because art is always pretentious.
And one reason I hate Indie so much is that unlike so called pretentious genres/movements/labels like Prog and Metal. The whole selling point of Indie is that its supposed to be un-pretentious. But is in fact the most pretentious music imaginable, in my opinion.
The only banRAB I'd say are not pretentious are banRAB that make music purely for entertainment. So no, AC/DC would not qualify as pretentious, in fact they are less pretentious than John Lennon, this dosen't make them better of course.