I have been following this story for years.  It is one of the rare occasions when one of my passions (comic books) crosses with my profession (law).  I have never been able to fully grasp how the Kirby Estate ever thought they had a realistic chance of winning this case.  The basic law in this area focuses on the expectations of the parties when the work was created.  I have been collection comics and reading every available history on them for close to forty years.  It has always been abundantly clear to me that all of the work created for Marvel during the sixties was work for hire.  The comic book industry was not fully formed during the thirties and forties which led to some of the confusion on rights questions for that era.  But by the fifties and certainly beyond, the rules of the industry had become fully established and the number one rule was everything was work for hire.  Jack Kirby knew that all of the characters he created and the artwork he was doing for Marvel belonged to Marvel as soon as he accepted his payment.  To me (and apparently the judge) this is the end of the story, there was no expectation of the retention of future rights on the part of either party.  Kirby was no babe in the wood in the industry.  If he had intended to retain any rights in the work he knew what was required contractually.  He did not even try at the time.

The reason why no one tried?  The comic book industry was the complete ass-end of the publishing industry.  At that time, no one considered the future rights of the work very seriously because at that time those rights had little or no value.  Reprints were unheard of (except as filler or when a deadline was blown).  No one was clamoring to make any comic book movies.  The stories and art were packaged into cheap, newsprint comics sold for a dime and only a hardy few even attempted to save them.  The value to an artist was his page rate and that was all the value anyone gave it at the time.

While I feel Marvel has some moral obligations to the actual creators (the living ones not their estates), I have never understood this case from a legal perspective.  Work for hire is work for hire.  The fact that twenty to thirty years after the work was created its value soared in ways never imagined does not change the condition under which it was created and the expectations of the parties at that time.