Depends on what you mean by ‘best’, really. I mean, I think – for all his faults – that Morrissey is a phenomenal lyricist with a good voice. But I know that he is not to everyone’s taste.
But I’m going to go out on a limb here and possibly embarrass myself.
On the basis of voice quality, I’m going to nominate Boy George. I think that the gospel-style sound he has, best represented by his small bit in ‘Do They Know it’s Christmas’, is excellent, and had he ever gone down this path, he would have made a superb jazz or gospel singer.
EDIT: I would also support scotroute’s Freddie nomination.