Winner: Rocket League
Rocket League's debut was unlike anything we've seen before. Prior to release there was some mild hype for its launch, if only because the premise of a soccer car game was intriguing. Within just three days of debuting on PSN and Steam it had over one million players and charted as one of the top five most popular livestream games on Twitch. It is unquestionably the most financially successful indie title of 2015, and for good reason; it's a game that prioritizes quick and accessible fun with simple entry but a high skill ceiling for hardcore competitive types. More than four months after launch, it's still a game that pulls in hundreds of thousands of players per day, and that's simply unheard of for a $20 title.