you know, I almost went with the obvious (JP) but then at the last minute I realized the one who really set them apart from the pack was Robert Plant. Page's playing and songwriting basically started a new genre that still exists today but Plant sold the product to the masses and Led Zeppelin wouldve never been nearly as big without him. Also when they broke up, we had a much more sucessful career afterwards, not that it has anything to do with LZ but he was the biggest star of the group, and that is what the masses seem to go for then and now.
my favorite member? Probably JP.