Yeah, I don't think there can be any question that Jimmy Page was the most important member of Led Zeppelin - he was the visionary, he started the band, he oversaw the recording and production, he wrote the lion's share of the music, and along with Plant, was the visual presence of the band. Having said that, at various times, especially onstage, it could be said that Jones or Bonham were equally as important just because Page, let's face it, didn't always have his shit together and Jones and Bonham seemed to always be a well oiled machine, whereas Plant and Page were the wild cards in concert.
Everybody has their favorites and the contributions of everyone including Peter Grant were monumental, but there's no doubt that Led Zeppelin was Jimmy Page's baby.