I don’t think the Justice League movie will be as great as The Avengers movie, and here’s why:
Haven’t Setup All The Characters
Avengers was great because we already knew most of the characters because they had their own films. The only new person was Hawkeye, but he had a big enough appearance in Thor to know introduce him and his skill.
DC has only introduced Batman, Superman, and Green Lantern, recently. They should make a Wonder Woman, Aquaman, Green Arrow, and The Flash, film before they decide to introduce them all into one film.
DC Characters Are Lame, Except for Batman
After characters, like, Iron Man, the X-Men, Daredevil, and more, the DC characters seem boring. Batman is the only exception. He’s never boring, unless he is played by Christian Bale.