I get the feeling people expect Superman to be more popular because its Superman. Its like he is expected to be the one on top. I can't argue with people who think he is more popular.
I suppose what i'm generally saying is. If you asked every single member on this site who it there favourite character is out of Superman/Clark Kent or Nightwing/Dick Grayson. Do you think it would still be Superman?
I have nothing against Superman by the way lol.