I'm going to take the pessimistic route on this one because what made the Avengers and
almost every Marvel superhero a success is how they were all true underdogs who can relate to the average inferiority complex of real people.
DC and the Justice League, OTOH, come from the perspective of "We were extraordinary individuals who became even better!" Batman is really the only one who can relate to Marvel's kind of audience...but maybe Superman can have some potential if they play off the plot of Smallville.
