Going to wade in here, because I am one of those for whom MoS was a profound disappointment. And while the movie did financially well on box office, that was all it did. Everyone went to see it opening weekend because "it's the next big superhero movie" and "it's the new superman movie" And that was easily enough buildup to make back its budget when most english-speaking movie goers go to see the same movie over a span of about 5 days.
By Monday morning, Man of Steel had effectively split DC and Warner's fanbase right down the middle. Traditionalist fans of the big blue boy scout like me hated it for derailing seventy five years of character work in favour of grimdark; and Modernists who enjoy the nu52 loved it because it made the character less boring and hyper-powered to them.
And because of that schism, it "underperformed." It didn't drive merchandising sales the way Batman Begins and Ironman did (those two movies being the archetypes for modern franchise launching). It didn't maintain its numbers for more than two weeks the way BB and Ironman did. And as we've seen in subsequent discussions, people aren't rabidly awaiting the sequel, so much as morbidly anticipating it. The movie did box office numbers, but in the much larger scope of building the brand for the DCMU and driving interest in licensed toys, games, and spin off media, the substantially larger financial market where billions are made compared to the 250mil that MOS did on screen; it has decidedly not performed up to expectations. (this is actually the same thing that happened to Superman Returns, it made bank, but didn't build the brand, which is why Brandon Routh ended up doing a one season sitcom instead of putting on the tights again)
I still see a lot of Bale-era batman costumes on the shelves for Halloween this year, but I see surprisingly fewer Cavill superman costumes, an indication of how it has failed to move merchandise.