I'll go with Sinatra, although I still like Bing a lot, and how his voice seemed to take maximum advantage of the not-too-great sound reproduction back in his day. Back to Frank, 'The Summer Wind' -- and the earlier the recording, the better; as with a lot of his stuff, the later versions are over-orchestrated and his singing so much less poetic & bewitching than early on.
Repeating myself, I still can't resist this trio either...