Obviously this is a very subjective topic, but while I'm a fan of Zeppelin, I prefer a few bands over them.
They have quite a few songs I just can't get into. Whether it's the pace, energy, or whatever, they just don't do it for me. I get it might be done well musically, but I'm not a musician, so I just go off of how it sounds to me. There are a few songs I like, but then they throw like a minute of moaning in the middle of the song, and it kinda kills it for me. Like in Whole Lotta Love or Dazed and Confused. I really like those songs, but that 1-2 minutes that they throw in there in the middle throws it off for me.
I honestly can't even pick who I think the best band of all-time is. I just have bands I love, bands I like, bands that I think have a good song here and there, and bands I don't listen to at all.