A number of folks out there are fans of interpretive singers...i.e. singers who don't write their own songs, but sing songs either written for them by professional songwriters or cover songs already made famous by other, earlier artists.
Nothing innately wrong with that, but I've always preferred singer-songwriters to interpretive singers. There's a certain authenticity to a song being sung by its writer that often, even the most gifted interpretive singer can't quite capture.
I also prefer musicians who play an instrument (or multiple instrument) as well as sing, especially if his/her instrumental prowess is of equal importance to the final product as the vocal.