It's a myth..
Dual ending myth [edit]
For many years a popular myth has persisted that in the Japanese version of this film, Godzilla emerges as the winner. The myth originated in the pages of Spacemen magazine, a 1960s sister magazine to the influential publication Famous Monsters of Filmland. In an article about the film, it is incorrectly stated that there were two endings and "If you see King Kong vs Godzilla in Japan, Hong Kong or some Oriental sector of the world, Godzilla wins!"[51] The article was reprinted in various issues of Famous Monsters of Filmland in the years following such as issues 51, and 114. This bit of incorrect info would be accepted as fact and persist for decades, transcending the medium and into the mainstream. For example, decades later in the 1980s the myth was still going strong. The Genus III edition of the popular board game Trivial Pursuit had a question that asked "Who wins in the Japanese version of King Kong vs. Godzilla?", and states that the correct answer is "Godzilla". As well, through the years, this myth has been misreported by various members of the media,[52] and has been misreported by reputable news organizations such as The LA Times.[26] Since seeing the original Japanese-language versions of Godzilla movies was very hard to come by from a Western standpoint during this time period, it became easily believable.
However, as more Westerners were able to view the original version of the film (especially after its availability on home video during the late 1980s), and gain access to Japanese publications about the film, the myth was dispelled. There is only one ending of this film. Both versions of the film end the same way: Kong and Godzilla crash into the ocean, and Kong is the only monster to emerge and swims home. The only differences between the two endings of the film are extremely minor and trivial ones:
In the Japanese version, as Kong and Godzilla are fighting underwater, a very small earthquake occurs. In the American version, producer John Beck used stock footage of a violent earthquake from the film The Mysterians to make the climactic earthquake seem far more violent and destructive.
The dialogue is slightly different. In the Japanese version onlookers are speculating that Godzilla might be dead as they watch Kong swim home and speculate that it's possible he survived. In the American version, onlookers simply say, "Godzilla has disappeared without a trace" and newly shot scenes of reporter Eric Carter have him watching Kong swim home on a viewscreen and wishing him luck on his long journey home.
As the film ends and the screen fades to black, owari (the end) appears on screen. Godzilla's roar followed by Kong's is on the Japanese soundtrack. This was akin to the monsters' taking a bow or saying goodbye to the audience, as at this point the film is over. In the American version, only Kong's roar is present on the soundtrack.
That's from Wikipedia...
