Big blockbusters will always do fine as long as they have brand recognition and merchandise/tie-ins. It's kind of silly to just look at box office grosses all the time, because in actuality that's not where the profit is; studios don't make blockbuster movies, they make highly-promoted multi-media, cross-promotional products, of which a motion picture is one component. You can lose money at the theatre and still come out in the black because you have home video, video games, Pizza Hut combos, Pepsi sales, a board game, action figures and collectible toys, posters, comic books, and maybe if you are lucky a cartoon or something. Blockbusters are financed based on this understanding and that's why they keep being made, even if the film itself doesn't make it's budget back upon initial release.

Unfortunately, that means there aren't really original blockbusters anymore. Avatar has been an exception, but there are a lot of other reasons for that. Star directors can maybe get an original blockbuster going, and a few random exceptions that prove the rule (Battle:LA, Sky Captain, etc., all financial losers). Otherwise it's all sequels, remakes and adaptations, for financial security reasons.