you eventually reach the moon, where the Dragon King (the final boss of the Moon game) is said to be waiting and holding the game world's goddess prisoner, which will bring about the end of the world of Moon. However, when you get there, you find that the goddess and the dragon are in fact two sides of the same being, neither of which are hostile in any way. The dragon / goddess says that you were brought to Moon to open a "door" and thereby save the world, but that your love is not sufficient to do so, and that the world is thus doomed to slip towards a dark future.
Then suddenly the hero appears, having hitched a ride on your rocket. He begins slaughtering everything in sight, gaining huge amounts of experience and quickly reaching max level. And you're powerless to stop him as he deals a mortal blow to the goddess. With its parting words, though, it tells you that there is still hope. That if you have a love that cannot be represented in terms of levels, you'll be able to change the prophecy and open the door when it next appears before you. As its voice fades away, it begs you again and again to open the door. The hero raises his sword and strikes you down, before collapsing into an empty pile of armour on the floor.
The screen shatters as the voice of the young boy's mother calls out to him, telling him he needs to stop playing games and go outside. Suddenly you're back in the real world, in front of the screen. As the boy once more moves closer to the screen, you're offered the choice of whether or not to continue. Highlighting yes places the boy in front of the television, the sounds of the game blaring loud in the background, while highlighting no causes his silhouette to move towards a door that has appeared at the side of the screen, to the sounds of birds chirping. And in order to get the good ending, you don't have to select continue, but instead have to opt out and instruct the boy to put the game off and go outside. It turns out the "door" the boy has to open in order to save the world of Moon from the hero is the one to the outside world. That if he truly loves the people of Moon with a love that cannot be defined in terms of levels, he has to realise that the way to help them is not by marauding through their world as some self-styled JRPG hero, but by turning off the console, going back to his own life, and leaving them to theirs.
The game essentially argues that if playing one of these games means being the kind of character who runs around murdering things and stealing people's stuff, then the only way to really be a real hero to the people of the game's world is by... er... turning it off and not playing at all. :'D It's a really interesting and sweet idea that is superbly presented in the game's ending, and it stuck with me waaaaay after the game had finished. It's also especially poignant when you consider that the game was created by former Squaresoft staff who worked on games like Chrono Trigger and the Super Mario RPG - basically it's their own response to and musings on the games they themselves had made to that point.