That's a very hard choice!
I picked Martin Gore, Depeche Mode is one of my favourite bands (even though I dislike their early stuff, but that's mostly the Vince Clarke-penned stuff like Just Can't Get Enough - yuk). Besides, his covers turned out to be quite wonderful (great choice of songs!) And while Dave is a great singer and frontman, I love Martin's voice at least as much as Dave's.
I like The Cure a lot too... but I only love some of their albums, while I strongly dislike some others. Robert Smith is a great frontman, but his voice... I only managed to find it tolerable with time.
Peter Murphy has the best voice out of those 4, and actually he is one of my favourite singers, maybe right after Moz. He was also a great frontman (and how memorable is his appearance in The Hunger?), although I'm not such a bug fan of Bauhaus. I prefer some of his solo stuff... he recorded a few of my all-time favourite songs: Strange Kind Of Live, All Night Long, Marlene Dietrich's Favourite Poem.
Of course, old Leonard is a great, great lyricist...and his voice perfectly matches his music. That sombre style is excellent in its own way, but I often prefer other people's covers of his songs... and he seems to be winning the poll anyway.
Shouldn't this be on Other Music?