I think Frank Sinatra was still singing well right up to the end. His voice was very distinctive but what made him more special was his phrasing and his breath control technique. If you listen, carefully, to any of his recordings you'll hear what I mean.
I loved Dean Martin. He had that "boozy" quality in his voice, always sounded as though he'd had a scotch or 8, but he never actually drank before a performance or during one. He always had a glass of amber liquid on stage, it was part of his act, but it was ginger ale - the booze came later. Very handsome, too, in his younger days.
What's the definition of a crooner? It used to mean someone who sang ballads in a non-operatic style so would you describe anyone who's around now as a crooner?