Diablo 3 has been available for just over a week, but was confirmed to have broken records by becoming the fastest-selling PC game ever. It sold 3.5 million copies in the first 24 hours, and has currently sold 6.3 million units. So what's the secret behind the success?

Digital Downloads

Diablo 3 is available through a boxed copy, but the game is also available digitally. Players could pay for and download the game before launch, allowing instant log-ins. It meant players didn't have to wait for a copy to arrive or queue outside a store at midnight, despite the server issues.

Aging Consoles

Interestingly, Nvidia CEO Jen-Hsun Huan said PC gaming worked in cycles: the platform becomes more popular as consoles grow older. For example, the Xbox 360 has its big releases - Halo 4 and Call of Duty: Black Ops 2 - releasing this year. Next year will probably be for next generation consoles.

Cheaper Games

A console game at launch could cost up to $60, whereas PC games are typically cheaper. Digital download services such as Steam all offer periodic sales, where all games are significantly reduced in price. June 2012 will bring the Steam Summer Sales, where gamers will buy dozens of games for the price of one.

Exclusivity

Diablo 3 isn't out on consoles. For now, the only way to play it is on PC. Call of Duty is multi-platform, so most gamers probably own a console supporting the franchise. With Diablo, and other genres such as MMOs, PC gaming is generally the only option. Even with games that are multi platform like Battlefield 3, the PC version supports 64 players - 32 versus 32 - and bigger maps due to increased graphical power.

Mainstream Genres

Diablo 3 is, at its roots, a role-playing game. Previously considered 'hardcore' by some through games such as The Elder Scrolls III: Morrowind, which let players do anything in no particular order outside of the main quest, franchises such as Mass Effect and games such as Skyrim made the genre mainstream. It's similar to first-person shooters: arena shooters largely moved aside for arcade shooters, such as Call of Duty, which has proven accessible.

The genre has also spawned rivals: Torchlight and the upcoming Torchlight 2 are rivals to Diablo, created by former Diablo developers Max and Eric Schaefer who co-founded Seattle-based Runic Games.