led zeppelin, dude
have you ever heard child in time??
ian gillan incredibly sucks now, but back in the 70's he was as good as god... there were no singers like him then, and im not sure if there are any now... he is like ten times better than any other guy of his time, and offcorse better than the oasis singer ian gillan had an amazing range, check DP live cuts, like made in japan and compare it to something like "the song remains the same" video, and you will find out the ian gillan is the god of singing
almost none of the DP singers sucked, they got fired or left coze noone could work with lord and blackmore that's all.

offcorse my vote to Ian gillan