I saw this post on rpg maker forums. The concept is intriguing. Basically it's like a chain story. In the story version you might write some paragraphs or a chapter before handing it off to the next person to continue. The poster on rpg maker forum suggested two ways to do it. One would be to create the story as a chain but then implement the game as normal. The other would be to pass the whole project along to the next person.
A different rpg maker forum had a "Swap in the middle" contest. One person starts the project and then gives it to another person to complete.
The idea is obviously hard to do and ever harder to do well. For a game version you probably need a well developed game engine with editor.