My thoughts exactly. I can't think of any towers that I'd team as iconic. The only tall 'structure' that has any cred is the Eiffel for being of that high a status. Might be plenty of well known towers, but nothing on par with the ESB or Burj KhalifaNone of them are really 'iconic' in my eyes.
If I had to choose one it would be the Shard come the end of this year due to all its media coverage before, during and after the Olympics.