This game's psuedo sequels make me want a special PS2 to play import games on. There are several games that are all the same thing as this, just not named the same. One features Gigantor and has you actually see his controller on the ground as you look up at his battles. Look at this video.
See, that's a sequel to this game. If no one else says it, I will. It appears to control and have similar enough content. Same developer, same style, and same controls? I'm iffy on the control part, but look at it. It's made by the same dudes and looks enough like this game to make me want to play it. Then there's this video.
It appears to be a prototype demo for the engine. Maybe not a full game, but it does answer one criticism I have. No giant Godzilla monsters are in this one. They are in the other Earth Defense games, but not this one. A bit about this engine, every building is destructible. Tons of people run around. And it powers some really amazing games. This and Earth Defense Force 2017. That game actually has two prequels that are available in europe, but not here. But that's another article for another day. Did you ever play Robot Alchemic Drive?