a good music critic...

A good critic is authoritative; passionate; suprising; open minded; entertaining; interesting; well-informed; committed; original; free thinking; indepedent.
A bad critic is uncaring; uncommitted; predictable; ignorant; negative; a show off; too fashion conscious; unoriginal; clichéd; too susceptible to hype.
(Adjectives taken from an unpublished survey of record buyers' use of record reviews that I carried out in 2006.)

(Simon Frith, taken from The Cambridge Companion to Recorded Music, p. 280)