Another major roadblock for player-driven communities is the developer's own eagerness for, well, developing. Just like with exploration, a developer can't force a desire upon players to create their own spin on their favorite game, but it can certainly suppress it by flooding the community with iterative sequels or even constant updates. In the case of Super Metroid, it was a unique game even within its own franchise.
This may be an unattainable utopia for developers on a tight budget and publishers on a tight schedule, but developers can still keep a community from splintering when an iterative sequel is necessary -- Valve's purposeful and gradual transition between Left 4 Dead and Left 4 Dead 2 is a prime example. Releasing updates and downloadable content instead of sequels is another way to keep a game's community in one place; this works particularly well for multiplayer games like Team Fortress 2, though developers must take care not to push out so many updates that they discourage player-created content.
Encouraging fans and avoiding these roadblocks is a good way to start a community, but in order to make the transition to self-sustenance, the community has to draw more people in on its own by garnering attention on its own merits. Super Metroid isn't the only game that gets attention for its achievements. The Elder Scrolls III: Morrowind's community, which creates mods that improve the game, made headlines nearly nine years and two sequels after the game's release with a compilation of mods called the 2011 Morrowind Mod Compendium.
But more important than earning the attention of the press, which is relatively sparse even for large modding communities, is garnering fans' attention. A developer can encourage this by giving fans a way to highlight and promote player-created content themselves -- this may be done with a website like LBP.me, which allows owners of games in the LittleBigPlanet franchise to discover, rate, and manage custom levels for the games.
In order to discover and promote quality content, however, a community has to create it. The most important thing is an accessible set of tools for players to use. Although SMILE was made purely by fans, the complexity of modern games demands developer involvement. The caveat is that any toolset must be either totally, undoubtedly complete, or its source code and the means to update it must be given to the community before the developer moves on. Developers of games like Morrowind and Half-Life have ensured this by releasing the tools they used to create the games in the first place.
Next, good documentation can help players use these tools and create better content. These can be in developer's hands at first, but must eventually become the responsibility of the community itself -- many communities, Super Metroid included, successfully maintain a wiki on their own.
Finally, the developer can encourage a collaborative culture by allowing and encouraging fans to release works in progress for feedback. By giving the community the means to create new content indefinitely and encouraging members to do so with the help of their peers, developers can aspire to foster the kind of community that is still around years after a game's release.
Although building a long-lasting community is no simple task, Super Metroid's organic, robust hacking community provides several key lessons for creating a self-sustainable game community.
While the steps above are one way to cultivate game communities like that of Super Metroid, they are neither comprehensive nor perfectly suited to every individual game. Use them instead as a guide for making players into fans, fans into fan creators, and fan creators into community leaders, and let them help you gain insight on what will work for your game and its community.