Based on my musical tastes, one might assume that I like Led Zeppelin more than Pink Floyd, especially since LZ was really one of the first heavy rock bands (many consider them to be the ancestors of heavy metal).
However, this is not the case.
Overall, I think Zeppelin was an extremely creative, talented, rock band. I consider John Bonham to be a virtuoso on the drums, and Jimmy Page and John Paul Jones are both amazing as well.
But unfortunately, it's that Robert Plant guy that gets me. Many consider him one of the best rock front men to ever live; he has terrific range and a unique voice, but I simply can't stand his vocals. I have tried over countless years to appreciate the man's sound, and I simply can't do it. I still listen to Zeppelin; I try to ignore Plant's vocals and appreciate the other aspects of some great songs, but because of Plant, I wouldn't consider LZ on my favorite bands, and thus wouldn't place them ahead of Pink Floyd.
And, uhhh, yeah Pink Floyd is really good and stuff, for various other reasons. %)