We saw My Big Fat Greek Wedding on a sea day in Jan 2003 (movie had probably been out about 6 weeks), and the theater was full. It's not the same configuration as a chain theater (like Lowes or Sony), but probably about the same number of seats. Most of the chain theaters are long and narrow, the Buena Vista theater is set up more like an old fashioned down town theater (the kind that had balconies), but is about 2/3 the size of the main floor area of the one we had growing up.
There's also a picture in the cruise version of the Passporter.