You are right about popular culture influencing media and visceversa. After all, media comes from popular culture, and those that stand the pass of time are those that, in some way or another, speak to our culture or caught the interest of their culture better. But I believe your examples are way out of mark.
The example of the dragon is not about greed being more prevalent or evil in depression era or the 60s, it was simply because Smaug is based on Scandinavian dragons, and those are always vile and greedy. Compare them with the dragons in Beowulf or Sigurd. Puff is simply a kids show dragon, and as such, is no different than Falkor and other children's book dragons. I am pretty sure the pile of gold was never a part of Puff's backstory, so to claim his was a representation of a more accepted greed is pointless. They are both dragons, but based on very, very different references and made to fit different roles, so to compare them is like comparing Barney and the T-Rex because "they are both dinosaurs".