Answer: LittleBigPlanet

In 2008, Media Molecule released a well-received platformer for the Sony Playstation entitled LittleBigPlanet. Players took control of a creature named Sockboy and, either on their own or with the help of friends in multiplayer mode, moved Sockboy throughout the roughly 50 levels of LittleBigPlanet.

Now if the game had just consisted of those original 50 levels, it’s quite possible it would have still been well received on account of fun and innovative play. What really built and maintained the fan base of LittleBigPlanet, however, was the easy-to-use level builder that made it dead simple for users to create and share their own LittleBigPlanet levels. User-generated content proved to be such a big draw to the game that by the end of 2012 there were over seven million unique LittleBigPlanet levels available for play.