I'm an old sentimental slob ...
My all time favorite ... only one version matters ... Nat King Cole:
http://www.youtube.com/watch?v=SOszvL9lgSs
A close second. So many good versions of this one ... Frank, Bing, Rosemary ... Luthur Vandross ... Coldplay, Kenny G (the video of that one really gets to me), Katie Melua does a nice version ... even Michael Buble. Guess I gotta go with the original Judy Garland:
http://www.youtube.com/watch?v=vSeHMjQEz3E