About 15 years ago, I was the lead programmer for a virtual reality ride prototype for Disney. We had added pterodactyls flying overhead.
The night before the demo presentation, I created a good pterodactyl scream by taking a recording of dolphins, reversing it, and dropping the frequency. Sounds strange, but I didn't have much time, and the effect was surprisingly good. A woman from marketing was trying the ride and raved that we got the pterodactyl scream just right.
I think foley too often gets short shrift as an art. You would think that in a medium where people are so eager to drop huge wads of cash on pseudoscience and marketing hype, the people who make sound effects that are even more believable than real-life noise would be heroes and legends.
Think about what good foley means to you. The arrival or departure of the TARDIS. Godzilla's roar. The sweepy red light on KITT. The "pew pew" of a laser gun that shouldn't really make any noise at all. The incongruous farty buzzing sound of a GAU-8 taking apart a tank. The crackle and hum of a light saber in motion. The "errr aka-chicka aka-chicka tullet-peppa tullet-peppa" of Ripley entering the Nostromo's computer core. The signature sound of a modem handshake. The ringtone of the very first mobile phone you ever owned.
It's just as important as the visual portion of a story, but gets much less respect.
While I think the bass rumble at the end is more true-to-life (if a 50 meter tall radioactive lizard can be said to be real..) the earlier films from Toho didn't have it.
Perhaps Toho would have added it if the recording & reproduction systems of the time could have produced it, I don't know.
Given that birds would be more closely related to Godzilla (as a dinosaur-like creature) I imagine he would have made more of a highly intense parrot screech rather than a lion/mammal roar. Then again: crocs have vocal cords apparently. https://www.youtube.com/watch?v=v7aOBcD3M70&t=32
I watched a documentary once that claimed the source (manipulated of course) was the sound of a metal gate opening.
Wikipedia says it was created via "...rubbing a resin coated glove along the string of a contrabass and then slowing down the playback" http://en.wikipedia.org/wiki/Godzilla
The night before the demo presentation, I created a good pterodactyl scream by taking a recording of dolphins, reversing it, and dropping the frequency. Sounds strange, but I didn't have much time, and the effect was surprisingly good. A woman from marketing was trying the ride and raved that we got the pterodactyl scream just right.