... in terms of music, eh?
The conventional opinion seems, in this age of endless TV 'talent'

shows seems to be some chick who warbles like Maria Carey, all over the octaves, or some lad whose been studying Robbie Williams for the last decade...
That isn't great vocals. For me, great vocals are about the stuff that comes from the heart, regardless of what your vocal chords can do, and how it resonates in the ears of the listener (if great lyrics are also forthcoming, so much the better...)
John Lydon
Tom Waits
Nick Cave
Shane McGowen
Iggy Pop
Henry Rollins
Ian Curtis
Leonard Cohen
Robert Smith
and yes, I'll include Mr Sullivan on this list, even though he does have a pretty fine vocal range... aint gonna get him on the X Factor, though!
that was a joke...