For me, personaly, Nat 'King'Cole wa the best male singer in the song-era. Maybe not so "thrilling", or flamboyant as others, that often gets this title thrown at them... -but for me; best SINGER - all hands down. I often joke: "Nat Cole was a mouth on two legs".
Until this very day, I still haven't heard anybody come even remotly close to Cole's impeccable use of pronounciation. That his voice-timbre was pleasant is also quite nice... and to top it off - he was even a darn good piano-player too! Fascinating guy.
Here you can find some of the songs he recorded. All transcriptions and/or arrangements thereof.