Typically we focus our gaming performance articles on AAA titles like Battlefield 4 because these are usually the games pushing the envelope and showing us what the latest graphics processors are capable of. But that's not to say we're not paying attention to the evolving free-to-play market. While Battlefield 4 started at $80 plus $30 for its China Rising DLC, you don't have to spend that kind of money for high-quality content.

World of Warcraft was considered a massive success with its peak of 12 million players (8 million today), yet it's dwarfed by World of Tanks' 1 million concurrent players and 75 million total users -- a following that is growing by more than 2 million a month. These kind of numbers aren't entirely unique to World of Tanks, either.

You can find more than half a million people playing Dota 2 on any given day and League of Legends has over 7.5 million players online during peak hours. Granted, registered users aren't the same as paying subscribers, but successful free-to-play developers can still extract money from a small percentage of their most loyal players.