This week, the Marvel Universe reaches a new plateau with the Hollywood red-carpet premiere of "The Avengers," which unites the title characters from four film franchises -- Thor, Captain America, Iron Man and the Hulk --  to save Earth from a cosmic threat. The only person who had a hand in creating all of those characters was the late Jack Kirby, a titan figure in comics, but his heirs weren't invited to the premiere;  their presence would be awkward considering…