I think you're overstating this, any number of simple games have been reproduced and virally spread. Tetris comes to mind. When that came out in the 80s, I was one of many who quickly produced a playable version and posted it to local bulletin boards. Similarly, many of the games discussed in Martin Gardner's and A.K. Dewdney's columns in Scientific American got pretty wide play (Conway's Life and CoreWar come to mind).

The scale and spread of these particular memes is larger and faster due to easier-to-use tools for cloning previous efforts (such as git/github), and more pervasive social media.