The secret ingredient, I suspect, is comfort. It may sound counter-intuitive to describe such movies as The Bourne Legacy, The Dark Knight Rises or The Avengers as “comfortable,” exactly — aren’t they all meant to be edge-of-the-seat experiences, after all? — but that’s exactly what they are. The overwhelming majority of successful blockbuster movies are the cinematic equivalent of comfort food, giving us exactly what we both expect and want with the minimum of fuss, and using characters or concepts to which we as an audience already have some form of attachment. Even once you throw out the sequels, prequels and reboots of existing movies, you still have all of the movies based upon toys we played with, comic books we read or television series we watched as children. There’s definitely an argument to be made for this comfort-led approach: The audience gets to know what to expect from their entertainment before they pay for it, and the studios are making less of a gamble with their investment in developing and making the movies, because, hey, known quantity and all that. Less cynically, of course, there’s an opposing argument to be made for the value of pleasant surprises and new ideas, but in almost every clash between culture and commerce, it generally pays to be cynical, sadly.
Reminds me of what "industry" (and certain clubs) look for from comedians too. Comfort food. Someone who's giving the audience a character they already know/get. Minimum of fuss. Unfortunately that leaves the more challenging/intriguing acts with a steeper climb.