I don't know. If you ever noticed, Godzilla has evolved over the years. He's actually become bigger, stronger and more potent (fire/radiation wise). In fact, the original breathed fire and it took time to melt a building. The updated one shoots white-hot streams of fire that can cut through building like butter.
I'm thinking of the original no so powerful Godzilla. Just like the original zombies could only shuffle around, now - they are able to run & climb and perhaps even swim in the future. Thanks for answering!
Godzilla is suppose to be an all powerful pre historical beast, that is so well adapted it is almost as if he is a god. Thus, no matter how strong men made thing is, They are going to make Godzilla even more powerful. It is same as human mythology, if we look at ancient story of gods, the gods are not all that powerful, but as human creation become better, gods also become more powerful. Same as superheroes, take a look at the batman, the original batman's equipment isn't all that fancy, but the equipment in batman movies and animated series today, are all military grade. It is estimated, to create a real life modern batman (training and equipment would be enough to build 2 US air craft carrier)