I really enjoyed the Avengers movie but I had to suspend a lot of disbelief, You had Black Widow martial arts skills and a gun no powers, Hawkeye sharpshooter with a bow ok fighter no powers, Iron Man a man inside a high tech suit which gives him enhanced strength, flight, the ability to fire energy beams and missiles, and enhanced armor, Captain America a highly trained combat soldier with enhanced strength speed agility and stamina, then you add then only real power on the team Hulk and Thor vs Loki (Thor's equal) with a cosmic sceptre and an entire army of Technologcally superior aliens. In the Justice League Movie you figure to have Batman a perfect human speciman of multiple forms of combat, detective, leadership skill with all the advanced tech money can buy, Wonder Woman a demi god the daughter of Zeus with super strength, speed, invunerablilty, flight, and the indestructable lasso of truth, Superman Superstrength, Speed, invunerability, Heat Vision, among other things, Green Lantern space cop with the most powerful weapon in the universe capable of anything he can imagine limited only by his willpower, Cyborg half man half machine enhanced strength abilty to communicate with technolgyy directly, white sound canon, Aquaman Superstrength, invunerability, a fierce warrior and leader, a high pwered trident and limited telepathic powers, The Flash the fastest man alive, able to break both time and dimensional barriors create vortexs of wind and energy and land thousands of blows in the blink of an eye. vs Darkseid an evil god and his armies from Apokalips Superstrength, Invulnerability, Omega Beams capable of pure destruction. Which battle is more even more believable I'd have to go with the Justice League. Yes only Batman isn't on a Thor/Hulk level power wise but Darkseid and his minions are a threat that matches that power. The Avengers are ridiculously overmatched, and it's even worse in the sequal which is probably why it didn't do as well.