As a pretty avid fan of jazz (modern progressive genres) and jazz fusion (the fiery, intense style, not the wimpy fuzak style), I can't stand Kenny G.
For a while, I didn't even consider him a jazz musician, so I was able to write him off and ignore him. But he considers himself a jazz musician, so, he is placing himself among the greats and should be evaluated as such. On that level, he doesn't hold up.
His intonation does not seem to be that great, and his improvisation vocabulary is pretty limited. As Pat Metheny said in an interview, "...rhythmic problems and his harmonic and melodic vocabulary was extremely limited, mostly to pentatonic based and blues-lick derived patterns". And, "he did show a knack for connecting to the basest impulses of the large crowd by deploying his two or three most effective licks (holding long notes and playing fast runs - never mind that there were lots of harmonic clams in them) at the key moments to elicit a powerful crowd reaction (over and over again). The other main thing I noticed was that he also, as he does to this day, played horribly out of tune - consistently sharp."
Then there's that track he did where he had the audacity to overdub his noodling over the great Louis Armstrong singing, "What a Wonderful World", my dislike for him as a musician, turned to dislike for him as a person.
Again, Pat Metheny, "But when Kenny G decided that it was appropriate for him to defile the music of the man who is probably the greatest jazz musician that has ever lived by spewing his lame-***, jive, pseudo bluesy, out-of-tune, noodling, wimped out, ****** up playing all over one of the great Louis's tracks (even one of his lesser ones), he did something that I would not have imagined possible. He, in one move, through his unbelievably pretentious and calloused musical decision to embark on this most cynical of musical paths, **** all over the graves of all the musicians past and present who have risked their lives by going out there on the road for years and years developing their own music inspired by the standards of grace that Louis Armstrong brought to every single note he played over an amazing lifetime as a musician. By disrespecting Louis, his legacy and by default, everyone who has ever tried to do something positive with improvised music and what it can be, Kenny G has created a new low point in modern culture - something that we all should be totally embarrassed about - and afraid of. We ignore this, "let it slide", at our own peril."
On the plus side, his son, Max Gorelick is a very promising technical-metal guitarist. He seems to have rebelled against everything about his father's music.