What artists do you think are the most neglected either critically or commercially? I'll say in the history of music in order to open the topic to any and all contributers.

Though I don't think Kurt Cobain is necessarily neglected, I think he definitely deserves a great deal more respect as a singer/songwriter, and as a genius generally. I'd rate him just below John Lennon in terms of originality, uniqueness and poetic ability. It also blows my mind that Radiohead is rated something like the 76th band of all time. I'd put them (and Thom Yorke especially) nowhere below #5.

Um, Radiohead will go down as one of the most OVERRATED groups ever. They have produced some of the most pretentious self absorbed drivel ever committed to airwaves.

I can think of a bunch of OVERRATED bands...

There really are so many talented people that never get a break.

The Melvins are the most underrated band in history! They're still kicking out some incredible, innovative sounds after 25 years, irrespective of any real commercial success.

Michael Gira is the first that comes to my mind, his solo work as well as stuff he's done with the Swans and Angels of Light, I could understand why most people wouldn't care much for the Swans but his AoL albums are amazing.

Some others I could say is Akron/Family, Built to Spill, Bedhead, Smog, Tom Waits, and the Brian Jonestown Massacre

My nomination for one of the top underrated or commercially overlooked bands would have to be The Velvet Underground. Their debut album, "The Velvet Underground and Nico" sold poorly upon its release and they were dismissed as too dark and nihilistic by the Summer of Love crowd in 1967. However, this same LP has since become one of the most influential albums ever recorded. I would say that The Velvets, like so many great figures in literature, were appreciated after their demise.

oh great prophet of musical lore, thank you for showing us the errors of our ways. of course - how could we miss it? - radiohead is truly drivel. nirvana was deritive of other, better bands. beethoven was an adolescent wanna-be. shakespeare was cliched. jesus was immature. what other light can you shine on our dim, cold world in such desperate need of towering intellects such as your own?

i like velvet underground a alot. some other thoughts:

my bloody valentine - i think that most of today's indie bands, knowingly or otherwise, are immitating "loveless."

tom waits - an afterthought for the public, but legendary and god-like amongst his peers.

neutral milk hotel - thrashed their instruments like an Arcade Fire without amps or pretension and, somehow, made something that sounded vaguely like a cat falling down a spiral staircase seem lovely and beautiful.

joy division - for better or worse, responsible for the current state of pop-punk.

pavement - just about everybody sounds like pavement today.

Funny!!! :-)
But I think Craig might have a bit of a point.
I started this discussion, but didn't put forth a choice of my own. So here goes.

Thin Lizzy would be my pick as one of the most criminally overlooked artists. While most people have heard 'The Boys Are Back In Town', when you ask them to name another song by them, blank stares are the most common result. The truth is, the band released a dozen albums of high quality rock, many of which feature songs that the afore mentioned 'Boys' couldn't hold a candle to. From their folky inception, right up until their NWOBHM inspired bow out with "Thunder And Lightning", the consistency of the releases never flagged.
Phillip Lynott has to be recognized as one of the most poetic of lyricists in the history of rock, as well as the epitome of 'tragic genius'. His song writing prowess(not to shabby as a vocalist/bassist either), coupled with the superb drumming of Brian Downey(as instinctive a rock drummer to be found), and a raft of high flying guitarists( Eric Bell,Brian Robertson,Scott Gorham, Gary Moore, Snowy White, and John Sykes), made for a potent mix of rock-n-roll heroics.
Whenever I am asked to suggest music for someone to listen to, be it a staunch pop fan or hardened rocker, Lizzy is always the group that instantly springs up. Never had a complaint from anyone who has taken me up on it either. Thus, I'm doing the same for whoever reads this. As perfect a 'can't miss' proposition as one will ever receive. Indulge and enjoy!!