i saw Page and Plant in some iffy early/mid 90s colab when i was 12/13.. even then and to my innocent ears it didn't quite cut it... Plant's voice must be completely shot, I mean, it was by the mid 70s wasn't it?
I never really got sabbath, give me a ruined Plant over Ozzy any day. Always thought Zep riffs had a lot more funk to them, and they explored many more avenues, pretty successfully too.
Page's solo's are often a load of scratchy nonsense though, 90% of the 'blues' tracks are tedious as hell.
As for John Bonham's bass inadequacies, I disagree, ok, there's obv. no sub on their records, but go and listen to 'Heartbreaker' or something : MONSTER TONE!
Can't say I've touched their records since i was 15/16, and they've spawned a lot of shit, but I don't know if all bands can be judged on that legacy. I think they were a great, fun, sonically powerful bad, and pushed the blues rock thing into much more dynamic and imaginative (and excessive!) territory.