Other... if we're talking singing ability, I'd have to go with someone like James LaBrie. That man's got a hell of a voice on him.
Out of the list you've provided, my vote would go to Ozz or Rose - more weight on "Front Man" than vocalist. When voting on that credential, James Hetfield rules all.
Edit.. speaking Lemmy, there's also the "Gimmick Guys" as I call 'em. Anselmo, Mustaine, and the Type-O dude. Not the best singing voices, but damn unique, which makes them good in their own right.
(Disclaimer: Gimmick in this sense is not a bad thing, nor is it a record company induced reason for sell out, it's just the name I've given it).
-Jeff