Crooners are my favorite vocalists, and represent one of my favorite pop music genres. The crooners I like the most are, obviously, Sinatra and probably the greatest, Bing Crosby. I cannot decide which is better however.
Sinatra had perhaps the better phrasing and breathing control. He had a real dark side to him - it wasn't all "Come Fly With Me." He cut some darker albums - "Sings for Only the Lonely," "Nobody Cares," and my favorite, "Where Are You?" Not surprisingly, they're the lesser-known of his albums, but "Where Are You?" which is all torch songs, is a real masterpiece, in my opinion. Still, aside from the torch albums, one of my favorite Sinatra recordings remains "At the Sands," which saw him at the top of his game, in my opinion. He and the Rat Pack really owned Vegas in the late '60s, thanks in part to mob connections I suppose, and his voice was at its peak. One of my favorite concerts of all-time, no doubt.
As for Bing, he was probably the coolest singer ever. People call him a baritone, but I sing in a chorus as a bass, and he sounds more like a bass to me, the way his voice sinks down an octave, and sort of glides back up. I really like his jazz recordings, or his work with the Andrews Sisters ("Don't Fence Me In") and I have a song he did with Les Paul called "It's Been a Long, Long Time" which is excellent. He really defined American standards, and without him I have no idea where pop music would be today. And of course, there's the essential Christmas duet with Bowie.
As for modern crooners, Bryan Ferry is obviously a great one. He really coos on his songs, and when he plays with Roxy Music you can't always hear his voice well live as a result. I love the way it shudders.

I read a review of a Morrissey album in Rolling Stone last year. They described him as slowly evolving into a "British New Wave version of Sinatra." The more I think about it and watch him, the more I think it's true. His vocal style, especially as he's aged, really emulates the crooners. He too writes phenomenal music like Ferry (he's a far better lyricist).
Ferry and Morrissey echo the crooners onstage as well. They go up there with their lounge jackets, outstretch their hands to the crowds, accent phrases with hand gestures, and grip their mic chords in a Sinatra-esque way.
Which crooners do you like?