Ron Barassi, Ivor Warne-Smith, Robert Flower, Garry Lyon and David Neitz would be my top 5.
Not that I saw Ivor W-S or Barassi play, but from what I've heard and read, they were outstanding.
Probably Flower and Barassi are the top 2, very difficult to split. Barassi had premiership sucess, and Flower was just an absolute legend.