However, when the mainstream press talks about Superman joining together with Batman, Wonder Woman, Green Lantern, etc, more often than not they make reference to if Man Of Steel can help launch an Avengers-like team. For instance, this recent MTV article, which reads, "Can 'Man Of Steel' Pave Way For 'Avengers'-Like DC Comics Series?"
Exactly, when did the Justice League become Avengers-like? Why didn't they just say Justice Leauge? This isn't a knock on MTV or the mainstream press (which often uses the same description), because they are just describing the Justice League in terms that the general public can understand.
Consider the irony of this situation, because it use to be The Avengers that were treated like the second class team. Back in the day, if a longtime comic book fan wanted to explain to a comic book newbie who The Avengers were, then an often-used description would have been "it's Marvel Comics version of the Justice League." That's because the defining concept of what a superhero team was to most of the general public was the Super Friends (i.e. Justice League) cartoon show.
Now, because Marvel Studios has so successfully launched their Avengers movie universe, it's The Avengers which define the concept of a superhero team to the general public. Even though DC Comics was the first out of the gate with the Justice League in the comic books, they will forever be compared to copying The Avengers in the movie world. To answer, the question in our headline, the Justice League became Avengers-like in May of 2012, when the The Avengers movie became a huge international blockbuster.
With the Super Friends cartoon show now a distant memory, the day is coming when even longtime comic book fans might have to find themselves explaining the Justice League to comic book newbies, as "you know, it's DC Comics version of The Avengers."