@IRENE46

Celine has excellent intonation, my problem with her is this "pinched" nasality she often uses, it's a very french thing I guess...also her upper belting usually is unbalanced and too heady, resulting in an almost falsetto sound. For reference to a balanced upper belting check out Patti Labelle or Monica Naranjo or Aretha in her prime.

Kelly Clarkson...I think she is very talented, but she can be very hit-or-miss...generally I do like her, and some times it's awful and strangled, so there are performances in which I'm impressed by her singing, and others in which I can't listen to her ("Since you've been gone" at MTV Awards, for example).
Other singers I also find extremely overrated are Leona Lewis (shakey intonation, bad breathe support which causes her low register to wobble out of control) and Jennifer Hudson (messy intonation, singing sharp a lot of times, unbalanced register coordination - like Celine Dion but instead of too heady, too chesty- ).

I like Gladys, Vanessa, Tina, Faith, etc but I don't know their repertoire very well...and Barbra and Donna I had mentioned already :)