I always think (and thought) of Bernard Haitink as the least controversial Mahler conductor, his recordings always impeccably paced and balanced. Not emotional or expressive in the extreme, but a steady middle way. And I mean that as a compliment. Sometimes I got the feeling people took him for granted, but instead he was a major contributor to the Royal Concertgebouw Orchestra. My only regret is that Haitink never went on to record any Sibelius or Prokofiev in general, or Vaughan Williams in Amsterdam. In any other way he was extremely versatile.
He will be missed, even though he retired two years ago...