Geeze guys, do we really need to start taking cheap shots at his widow?  

In his final years Dave was in a bad place financially and his health was a mess.  Maybe it doesn't justify bitterness or misplaced anger and blame, but it provides context.  

I've also read interviews where he took a more equanimous perspective.  He admitted that he cost himself a pile of X-Men royalties by choosing to leave the title for the second time to do Futurians for an indie publisher, just at the X-Men royalties were really starting to take off.  Like all creators he had dreams of characters he owned becoming a big success, but the indie publisher crashed and burned after a few issues.  And X-Men turned into a royalty jackpot for Claremont and various artists in the latter half of the 80s, which he acknowledged he could have been one of.

The John Byrne I've seen on these forums is always praising and encouraging other artists, and only rarely says anything disparaging any of them. 

Case in point: I think most regular visitors to JBF could quickly name from memory at least a half-dozen or more artists whose work JB admires... people like Dave Cockrum, John Romita JR, Jack Kirby, Neal Adams, Wally Wood, etc. But try to name the artists he's rubbished, and it gets tough - I've only seen him overtly disdain Rob Liefeld.

Dave Cockrum was a very talented man. Unfortunately, one of the hardest things for someone with talent to accept is anyone who has even more talent than they. 

Especially if that someone is quicker, far more prolific, arguably much better, and has talent encompassing a far broader area of the creative process... like JB.

JB's career reminds me of the movie Amadeus In many ways...and not only because there are many Salieri-esque critics in the industry, ready to surreptitiously tear down his work and his character - but also because, as I understand it, both the movie and the popular conception of John Byrne competely distort reality: both Mozart & Byrne worked very hard to utilise thier talent to get to the top of their respective professions.

In his lifetime, Dave never got the accolades--and definitely not the financial rewards--that he should have for creating the New X-Men. Relegated to B-list projects and fill-ins when he even got calls from editors, in poor health and broke with no retirement plan or savings or company healthcare, not considered a Hall of Famer until years after his death...all while seeing the X-Men's fame grow exponentially in comics, then the cartoon series, the toys, the movies...who wouldn't be hurt and upset by that?

Some of those negative feelings may have been pointed in the wrong direction, but it's not hard to see where they came from. 

The irony of this to me is that one of the main reasons I know better now is because you schooled me.  Your comments about Dave and his artwork over the years are a big part of what made me reevaluate and realize that I wasn't giving him near enough credit.

Yes, Dave had in his head a version of JB that priviliged and amplified the bad sides, probably both real and  imagined, and minimised the good ones, both of the man and the artist.

That certainly largely came from his biterness, maybe also of things between him and JB that are none of our business (i don't know), but while his wife Paty is a nice person, she is also a crazy one that fueled the fire. Paty also did that (to a lesser degree) to the relation between Dave and Shooter: Jim always spoke of Dave as of a friend, but Paty loved to work with Stan and didn't welcome Shooter* at all (Jim seemed to wonder why, when i suggested that reason on his blog, he told me it may be true.) Dave was silent about Shooter, i don't remember him saying good or bad things, only talking of the professional aspect. / *or if i understand well, any other EIC, but maybe Shooter even less. 

Cockrum no doubt came up with a lot of ideas, but in regard of artwork, Byrne is the best X-Men artist the comic ever had in my opinion. Not meant as flattering, it's just the way it is. 
Even if there have been some interesting runs during the years, the Byrne-Claremont run was for me the best run of the X-Men, and that's not just because of nostalgia. There is a reason why the movies have mostly used material from this era.

(Also, that was before X-Men turned into nothing but a metaphor and allegory for bigotry, racism and discrimination. And eventually gave us more mutants that was possible to name, draw or come up with individual powers. Something that previously had been restricted to people like Eternals and Inhumans, which unlike mutants were not isolated individuals.)