Bossa Novas are good after a stressful day, or when you want to relax and get away from some bruising computer games.
To be fair, most jazz artistes will have to make a living, at the end of it all, it has to be commercial.
However, the style of each individual singers will show each person's interpretation of some old songs, or their attempts to transport you to another world. Their success will depend on people like us, who will have our own inclinations.
Personally, I would prefer to enjoy the style of most lady singers, as I find their voice more soothing. Amongst the male singers, I find Tony Benetts and Ron Kaplan voices to be good too.
Stacey Kent has a nice style, much like Sheena Easton effort, as well as that of Dianna Krall, but a little different from Laura Fyggi.
Try this site for some good jazz cuts:
http://www.ladysixstring.com/downloads/index.htm