When I think of repetitive songs, I really don't think of "Who Are You". Sure, the chorus repeats a line, but compared to the billions of other songs with repetitive choruses it's not that bad. Not The Who's best by far, but not hideous.
But as for songs that still annoy us, I would second "All Star", which I hated before it was cool to hate it. And in more recent musical releases, if I hear Katy Perry's inescapable "Hot or Cold" one more time, I will not be responsible for my actions. It's not a particularly horrible song, but it's STILL FREAKING EVERYWHERE.