[chiph]

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.

[marquis]

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