Well it seems the new line of conversation is "Whoever came first is best!".

First of all, thats not accurate. The Who and Zep both made music during the 70s, and Zeps was much better. Popular opinion, critical opinion, and every other opinion constantly put Zep on or near top and the Who somewhere down the list of best rock and roll bands.

Second, all of the members of Zep were seasoned veterans of the 60s. Simply because Zep was not formed doesnt mean all the members werent "on the scene" during that era.. do you think all that talent came out of thin air? Page, Bonham and JPJ were all known and recognized in the community as great artists. Plant was a little more obscure. Bonham was actually fought over quite a bit. Zep may have come after the Who but its members were veterans of that era just as much as the Who.