Top 5 Rock n Roll Vocalists

Both as a writer and a vocalist... Frankie Miller

a couple i'll toss in:
steve marriott (small faces, humble pie)--the great white soul shouter
jim james (my morning jacket)--i've got very mixed feelings about their recent records, but the guy has an incredible, hypnotic voice
robin zander (cheap trick)--always though he was the best of the classic rockers. mega lung power.
alex chilton (box tops/big star)--definitely an acquired taste, but a really expressive, unconventional singer
ian curtis (joy division)
david thomas (pere iubu)

Robert Plant
Freddie Mercury
Thom Yorke (Radiohead)
Mike Patton (Mr Bungle, Faith No More, Tomahawk)
Little Richard

Honorable mention: Chuck Berry, Roy Orbison,Jerry Lee Lewis, Ian Anderson(Jethro Tull), Ian Gillian(Deep Purple), David Bowie, Peter Gabriel(Genesis) , Maynard (Tool), Mick Jagger, Jello Biafra, Greg Lake

I agree with some of the usual suspects, in particular Robert Plant, but I never liked Freddy Mercury's singing.

Roger Daltry would also be a frontrunner for me. I'll throw in one wildcard, who has a very unique voice that I really like; Steve Winwood. He lacks the charisma of the great rockers though.