There are no 1.78:1 (16x9) film sources, only video; so no unmolested film content will utilize the whole display area.
16:9 film stock may not be that common these days, but theatrical films that were recorded digitally (or are CG) might 'natively' be in a 16:9 AR. Also, I believe some older film formats
were 16:9 (and other ratios, including 4:3, were also in use in Hollywood at various points.)
And then you have
really wacky cases, like the Harry Potter films. If you look at differences in the widescreen (16:9) and 4:3 DVDs, apparently it they were 'filmed' digitally in something like 2:1 and then cropped differently for
both the 4:3 and 16:9 cuts -- the 4:3 is
not pan-and-scan, but actually a different set of cuts from the digital negatives!
Some info (I can't find the site that discusses the Harry Potter movies right now):
http://www.rexer.com/cine/oar.htm
But yes, the issue you are having with King Kong is that the film is 2.35:1 and your TV is 16:9 (1.78:1). If you were watching it on a 4:3 screen, the black bars would be much bigger.