A "dungeon master" type of project would rather work, where you have a basic game/ gamesystem and peole can easily use an editor
to draft new quests and location (and even events) that can be
plugged into such a game.

Similar to the dungeons in neverwinter nights.

But a whole game from groud up would fail.
As you need just a core group of 5 to 6 dedicated people
rather than dozents of unmotivated contributers.