I wonder how many of those two million paraders were just tagging along/bandwagoners, though (both in Chicago and Philly). I know there should be more "hardcore" hockey fans in both of those cities than there are in LA, but if I was given a choice between a parade with 300k dedicated and passionate fans and a parade with 2 million fans of "mixed" dedication, I'd go with the former. I know this probably isn't what's being compared here, but just putting it out there.
In any case, 300k seems like a huge number to me, regardless of what the turnout was in other cities.