10. Prison Architect
Units Sold: 1.7 million
Metacritic Score: 79
Prison Architect ranks 10th in our list of most successful indie games of all time. It is a simulation game created by Introversion Software. In the game, you construct and manage your own prison, controlling various aspects of the structure. You hire staff, guards, workers, and hope to control the prisoners. The game was successfully crowdfunded which is a testament to its popularity among gamers.