A few points about the dragons in Game of Thrones: 
  1. I have a hard time believing they could possibly fly.  Airplanes fly because they have gigantic wings and are propelled by powerful engines.  Birds and bugs fly by flapping their wings to lift their lightweight bodies.  Birds have hollow bones, and feathers weigh almost nothing.  Dragons on the other hand are big, bulky creatures with scales and completely aerodynamically useless tails.  The wing size required to lift a body that big would most likely make them too big to flap.
  2. Fire doesn't automatically make things explode.  When the dragons are flying around and fireblasting the ground and buildings, wooden and brick structures are shown exploding into bits.  In reality, it would be like spraying something with a hose.  Maybe a firehose, but still not a method of destroying solid things.
  3. Ok, dragons fly.  Ok, dragons breathe fire.  But where is this fire coming from, and how is it produced?  Is it like a propane tank, or is the fire created as needed by mixing chemicals like an epoxy gun?  Either way, surely there's a limit to how much fire can be created in a specific amount of time.  Destroying an entire city is a bit out of the question, because the dragon would need to refill or recharge.
Or, you know, it's magic. #entertainment