Thor and the Hulk may be big names but it is really the Scarlet Witch who is the most powerful avenger with those reality altering powers (If she cries out "No more JLA!!!"). But if the Flash takes her out early in a fight, then JLA will surely win the fight. Superman, WW, MM, GL have enough raw power to take on the likes of Thor, Hulk and Iron Man. Not to mention the Flash, who can easily solo. I'm not a biased DC fan, but the members of the JLA are way too powerful.
Let Batman and the Captain fight on for the rest of eternity!