Yes, Kevin, the Trio really amazes me, and I have compilations of their recordings, which I prefer to the material Nat did when he became a "star".  Nonetheless I agree..comparing his voice to Sinatra...no contest, in my opinion.  The King was/is smoothe as satin..simply the best, and he wipes the floor with all the other crooners also including Perry Como, Tony Bennett (?sp), etc...We won't even mention Harry Connick Jr. (shit, I just did), cause he really is a total FAKE.

Now...that being said, what do you think about Johnny Hartman?  Many years back, I got the famed recording he did with John Coltrane, then went out and found some of his other recordings (which aren't nearly as good...), still I found him to be one of the great, not as well known Jazz male vocalists of that era.  
Then there's Big Joe Turner, and actually I really like Jack Teagarden's voice..then there's Louis, but that really is a different sort of scene.   Yep, Nat...clearly "the MAN".

Thanx boss, for mentioning him,

Gene