As far as this type of genre goes, I'd put it as the equal of Jaws or any of the Lord of the Rings films, mostly because I thought LOTR dragged in places, whereas even though Kong is three hours, there is not one boring or unneeded second--and this is coming from a man with a ridiculously short attention span.
I don't know if you guys have it, but here in Australia we have "gold class" cinemas. They're like a few bucks more and you get these cool sofa's to sit in, whats more its 18+ only, and they serve booze.
Me and my girl went and saw King Kong in one of these Cinemas - Complete with a fresh cooked pizza half way through the movie, and a couple of beers for me. And I gotta admit it was one of the best movies I've seen in a long time - 3 hours that went by in a flash. Great film.
Fair enough: I saw this movie and it is awesome, and I'm a fairly harsh critic of movies, as I see 50+ a year in the theater.
The end is definitely sad, although possibly moreso to me than others, because I find animal death far more disturbing. If I had to choose between shooting a dog and some dude, I'd shoot the guy everytime... call me crazy.