There's no way I'd ever put Kenny G and Metheny in the same category. Metheny has been on the leading edge of Jazz for 30 years, he's defined a sound and is definitely a legend of the jazz scene. Seriously, he's played with Ornette Coleman, Scofield, Joni Mitchell, Wayne Shorter, Herbie, Charlie Haden, Jim Hall, Roy Haynes, Dave Holland, the list goes on and on and on and on and on.
He's all over it.
I love the start of this interview:
http://www.jazzoasis.com/methenyonkennyg.htm
He critiques Kenny G on a technical level, then goes on to talk about the afore-mentioned youtube clip. His biggest issue with Kenny is his overdubbing of Louis Armstrong's tune.
Polly, sure there's worse music out there, but there's certain lines you shouldn't cross to make a buck (and I'm sure you'll agree there was nothing 'artistic' behind Kenny G's Wonderful World, it was purely financially motivated).