Godzilla would be a very hit or miss theme for me. I'd want more of a King of Monsters style game where you're battling other Kaiju monsters while causing destruction in various metropolitan cities. If you've ever played any of the Burnout 3: Takedown, a bit like the crash mode where your score is tabulated by the amount of destruction you've caused. I've been toying around with an unlicensed game with monsters from various cities: Godzilla (Tokyo), King Kong (New York), Werewolf (London), Gargoyle (Paris), Minotaur (Barcelona), etc.