It's the most financially successful Godzilla film to date. There's a lot of love for it on the imdb user reviews, but I thought it was only okay.
Firstly, some historical background. You might be wondering how King Kong reached Japan. The answer, of course, is "money". Thirty years after the original film, the rights owners, RKO, had zombified. They didn't make movies any more, but they were happy to license the rights to anyone who paid them an eye-watering fee. The man who did the effects for the original King Kong, Willis O'Brien, was going around Hollywood at the time with an idea for King Kong vs. Frankenstein, but RKO's price tag meant that none of the studios were interested, plus of course this was 1960 and fifties monster movies were (thank goodness) on the way out.
However there's one country that'll always be willing to pay insane sums of money for stuff that no one else in the world would touch with a bargepole. Hellloooo, Japan. O'Brien sold his idea to John Beck, an independent producer, who in turn sold it to Toho. Kaiju films were still going strong in Japan, so Toho were excited by the idea of doing their own King Kong, even if it meant paying 200,000 dollars to RKO. O'Brien's idea eventually became multiple films, with Godzilla shoving aside Frankenstein in the "vs. King Kong" battle, which in turn eventually spun off Frankenstein Conquers the World
There are also other Japanese King Kongs. Five years later Toho released King Kong Escapes, while there's a lost Japanese film from 1938 called King Kong Appears in Edo.
For what it's worth, Toho's financial gamble paid off. King Kong vs. Godzilla went berserk at the box office. RKO's fee by definition made this a big-budget movie, so Toho backed their judgement and gave it everything. It was in widescreen colour with stereo sound and the original director, Ishiro Honda, despite the fact that the big reptile himself hadn't appeared on-screen for the best part of a decade, since Godzilla Raids Again
. After this, though, the sequels would go on forever.
So, the film itself.
It's lighter in tone than even Godzilla Raids Again
. I wouldn't argue if you called it goofier. Ichiro Arishima looks like Groucho Marx, with glasses and a moustache, and he's the film's comic relief with his stupidity and coin-toss decision-making. He sends two of his subordinates off to Skull Island for the sake of what looks like a children's science program on TV, while his main reaction to Godzilla's arrival is annoyance at the lizard hogging all the newspaper headlines. This movie is actually a modest parody of commercialism and the TV industry, borrowing heavily from the salaryman comedies that at the time were making Toho far more money than their kaiju films. Arishima in particular had made a career from salaryman comedy.
On this level, the film's mildly amusing. I'd put it no more strongly than that. It's light-hearted and you can see the bits that are being played as jokes, but I didn't laugh.
The consequences for Godzilla, of course, are that he's almost kiddie-friendly. He's not scary any more. His roar is more high-pitched, his costume's been redesigned and the first thing he does on seeing King Kong is to have a disco dancing competition with him. This was deliberate from Toho and from Eiji Tsuburaya (director of special effects), although it caused unhappiness in the production team. Ishiro Honda said years later, "I don't think a monster should ever be a comical character." Commercially, the move worked. Artistically, it makes the film feel lightweight. I didn't really care about what was happening, although I must admit that Toho did well to sell me on the monster smackdowns. You see, I was assuming that the fight would be a walkover. Godzilla is the nuclear bomb on legs. King Kong in contrast got killed by biplanes and should have been much smaller than his opponent. However here they give King Kong a cool rampage of his own, including carnage with a train, and eventually it seems reasonable that the two could go at each other on even terms. Godzilla has flamethrower breath, but King Kong shows more intelligence, so that's a fair fight.
Of the two monsters, Godzilla looks better. He's always been a rubber suit, so you're never comparing him with O'Brien's 1933 stop-motion animation. His latest suit design's quite good and I particularly like the effort they put into bringing alive his tail, although the glowing blue dorsal fins are weird.
King Kong, though, is a cheap-looking gorilla suit. Personally I didn't think he looked too bad, but monster movie fans apparently think he looks terrible. Toho's promotion department agreed, incidentally, never using photos of their own gorilla suit on posters and instead always cut-and-pasting 1933 pictures instead. He doesn't look realistic, but I got mildly fond of him. The actor inside his suit is sometimes using the body language of chimps rather than gorillas (e.g. the raised arms), while I don't think those electro-paws after being electrocuted make sense.
As for the story, it's at best passable. An American submarine shows up, to the horror of anyone who speaks enough English to realise that we're about to get amateur performances from foreigners who happened to be living in Tokyo and fancied earning a bit of pin money on the side. Fortunately the English-speakers all die when they run their submarine into an iceberg (in open ocean, while not being chased by anything), get stuck in it and then discover that Godzilla was inside. I believe the technical term is "loser". It's later (correctly) predicted that Godzilla will travel to Japan all the way from the Arctic Circle, because he loves his home. Another mysterious insight into dinosaur psychology there.
Meanwhile Ichiro Arishima is sending two subordinates off to Skull Island (here called Phoenix Island) in search of anything that will get better ratings for his TV show. He's later surprised when he gets into official trouble for trying to ship a drugged and bound King Kong into Japan without telling anyone. What a dork. Skull Island itself has lots of spear-waving natives, some of whom are obviously Japanese actors in blackface, yet it's also the best part of the movie. It has a gruff chief native and a black woman who's basically an extra and yet shows the only realistic fear in the movie when she ends up getting menaced by King Kong.
The natives also dance, a lot. In bikinis. This is good. Between them and Godzilla's disco dancing, I'd love to see a fan edit of this movie with the Saturday Night Fever soundtrack. However this would also be a crime, because Akira Ifukube's score gives grandeur and scale to something that's quite silly.
The American cut of this film doesn't use Ifukube's score, though. It's apparently the most hacked-about of any Godzilla film in America, which is saying a lot. They took out the comedy, you see. This is ambitious given that the film is a comedy (although not a particularly funny one), with the giant rampaging monsters being almost a subplot.
Is it worth watching? It's okay. Is it good? It's harder to go along with that one, but it did its job and put an awful lot of bums on seats. Even today, it's still quite popular. Personally I wouldn't say that I either liked or disliked it. King Kong and Godzilla are kind of fun, although the film's best monster is actually a giant octopus. It'll help if you're charmed by cheap special effects, e.g. the toy tanks. The Japanese actors are okay, but the girls are hot and one of them is Mie Hama, who'd be the main Bond girl in You Only Live Twice. There's a Hexachromite Moment with strong string that might, just, possibly, be used again later in the plot. The end of the big title fight is so undercooked that I stopped and rewound on the assumption that I must have missed something, but again, that hardly matters. (Hands up anyone who thinks the indestructible nuclear-metaphor prehistoric sea monster might have drowned.)
It's a blockbuster, basically. That's what they looked like in Japan in 1962. Any difference between this and Michael Bay's Transformers movies is merely cosmetic.