In long term history, Godzilla is the most Famous of All Japanese Kaiju. This particular Godzilla (Or Zilla as it has come to be called.) is from the Godzilla from the Animated series that served as a sequel to the ill fated 1998 Devlin/Emmerich movie.
Zilla appears as he did in Godzilla: The Series.
Zilla is one of the most powerful Kaiju on Earth (It was never truly shown if he was ever as powerful as the True Godzilla). He's a valuable ally to the heroes. Mostly called in destroy enemy Mechs or Kaiju.