You're right about the Batman comparison. Since the Simpsons have been around for 18 years, everyone already knows about them so marketing had to be approached differently. Having the show on the air everyday is free advertising, so they could afford to do other things, like the
Kwik-E-Mart experience. They had to keep the movie away from critics, not because the movie was bad, but because they didn't want the plot leaked and the jokes ruined. There was a time when The Simpsons went through an embarrassing phase ("Do the Bartman" says it all). But I guess it evolved into something better and more timeless. I still enjoy the show but refuse to buy the DVDs. It's on like twice a day so why bother paying for it?
The budget for the movie was $75 mil and the animation really looks stellar. You get to see every single resident of Springfield, it's awesome.
