Indeed, Deep Purple had two recognizable hits: "Hush," from 1968, and "Smoke on the Water," from 1973, both of which peaked on the pop charts at Number Four. (Their other Top Forty hit, strangely enough, was a cover of Neil Diamond's "Kentucky Woman," which slithered up to Number 38 at the tail end of 1968.) Those songs had just three of the five band members in common.
My intuitive sense is that a group with so many shifting members couldn't possibly be among the greatest of all time. Was it possible that Deep Purple was immortal with Rod Evans handling the lead vocals, and then again with Ian Gillan doing the honors? The Beatles, you know, had four guys ever. I bet you could name everyone who has ever been in the Rolling Stones. Sure, it's unfair of me to compare Deep Purple to the greatest bands in pop music, but no one has ever accused me of being fair in these little essays.
There have been many Temptations over the years, but they had a small core of lead singers along the way, and were heavily producer-driven anyway. Fleetwood Mac may make a better comp for Deep Purple, but everyone knows the Buckingham-Nicks-McVie-McVie-Fleetwood lineup is the reason they're in the Hall of Fame.
The strongest argument in Deep Purple's favor is that there are a lot of hard rock performers, especially guitarists, who have a tremendous amount of respect for them. Tom Morello wrote the article on Deep Purple in the Rock & Roll Hall of Fame nomination booklet, the only musician to do that for any of the nominees, and I place a lot of weight on that. (Morello calls them the third-best heavy metal band of the 1970s, which to me is like being the third-best wide receiver in the AFL [Art Powell, probably].)
Slash has been quoted as saying, "How can you not induct Deep Purple?" Lars Ulrich of Metallica told rollingstone.com, "I got two words to say: Deep Purple. That's all I have to say: Deep Purple. Seriously, people, Deep Purple." That's more than two words, but you don't mess with Lars.
Tom, Slash, Lars, you guys are all free to vote for Deep Purple, if you have a vote, and I'm all in favor of you having one. I'm sure the first riff you all ever played on the guitar was "Smoke on the Water" (yes, I know Lars is a drummer, but I'm sure he can play "Smoke on the Water" on the guitar). Writing an extremely recognizable and easily playable riff isn't quite enough for me, though. I vote NO for Deep Purple.