Year: 1996-Present
Platform: PC, Mac, 
Publisher: Blizzard

While Diablo may seem limited in terms of depth, customization, and non-linear gameplay when compared to other entries on the list, the series perfectly crystallizes how an action role-playing game can be both engaging and appealing to a larger audience.

Some role-playing games have the tendency to be remarkably exclusive, but the Diablo series manages to make hack n' slash dungeon crawling accessible thanks to an intuitive and welcoming user interface. Combine that with the universal appeal of a 'go kill the Devil' narrative and you've got yourself one of the most popular RPGs ever coded.