If you have to resort to small sample sizes, month, seasons, # of $300+ million films, over yearlong trends, then of course there's going to be variations and no clear trend. From what I can tell, see
http://www.boxoffice.com/statistics/yearly, ticket sales have basically been flat the last 5 years, which pretty much makes the argument that box office hasn't been affected by the recession. And, really, people want entertainment and movies are one heck of a value. Especially compared to live entertainment.
Heck, there are 3 huge blockbusters in 2009 already and we're not even to Memorial Day. Avatar, Alice in Wonderland, and, yes, IM2. You can also toss How to Train Your Dragon, Clash of the Titans, and Shutter Island into the success category.
The ideas that IM2 is not a success or needs justification because it's not going to do $400 million both seem off base to me. IM2 is behaving like a sequel to a popular film. Heck, of successful sequels, very few blow up to significantly greater grosses, TDK, Transformers 2, and POTC, basically. Harry Potter, LOTR, James Bond, Bourne, Star Wars, and Spider-Man were all essentially flat compared to their first films in their current incarnations. That didn't make the latter films failures of any sort.