Can Justice League be as huge? No. For a couple of reasons.
The initial Avengers movie was if anything an over achievement. So much so that even it's sequel, which was a success as well, couldn't even match the heights of the initial movie. As it's been pointed out, I'd be highly surprised if any of the remaining Avengers movies actually surpass their original in terms of money or popularity.
Another reason why Justice League I don't feel will be as successful is simple, DC & WB have tried to create in 2 movies, what Marvel created over I believe it was 5 movies: A universe. That's one of the reasons why the initial Avengers was so much of an overachiever. It brought together people that liked Iron Man 1 & 2 , Hulk, Thor, Captain America. I'm sure comic fans would have seen it regardless but there are general audience members that would have seen maybe one of those movies, liked it & thought I'll go see Avengers since xyz is in it. The Marvel universe is also I'd say more children friendly, Man of Steel & BvS carry more of an adult tone I feel, both films take themselves more seriously than I feel they probably should.
DC went about it all wrong, Man of Steel I feel gave the universe a credible opening, they should have then went with a sole Batman movie establishing the Batman of this universe with the ending of that movie being what was the start of Batman vs Superman ie Bruce being in Metropolis during the Superman/Zod confrontation. Then add in a Wonder Woman, Aquaman, Flash solo movies with perhaps cameos from Batman, Superman or even just acknowledging in some capacity that they exist in the same universe THEN Justice League should have come.
Batman vs Superman really could have launched the universe in 1 movie & completely caught up to Marvel which is no doubt what they wanted to do cutting all the corners in the process, the angle had so much promise but they really did just try to do too much, too soon focusing more on trying to cram all sorts of information in 1 movie to establish things rather than focusing on just trying to make it good.
The DCU is still salvageable I feel as despite all BvS's flaws & disappointing ending, the ending itself despite how it was executed has left me with anticipation on what will happen next.. but I'd honestly be surprised if Justice League will be able to be as 'huge' as the Avengers. It's actually not something that concerns me, as long as I find the movies enjoyable I couldn't care less if the critics dislike them or they don't make as much money as the Marvel counterpart.