Blizzard Entertainment Inc’s Hearthstone: Heroes of Warcraft has helped popularize the rapidly expanding collectible card game (CCG) video game genre, and a recent study by SuperData Research Inc. found that Hearthstone sits at the forefront of a genre that brought in over $1.2 billion last year.

“Collectible card games have been tremendously popular for a long time, and in its transition to digital has managed to reach a massive audience,” said SuperData analyst Carter Rogers. “It’s a fascinating category … because it combines micro-transactions with strategic, competitive game play. Collectible card games have remained popular through the years and will continue to be a source of inspiration for the industry at large.”

According to SuperData, Hearthstone earned over $173 million in worldwide revenue in 2014, more than the next three highest earnings CCGs combined. Rogers points to Hearthstone’s ties to the Warcraft franchise as one factor in its success.

“The unprecedented success of Hearthstone compared to its peers is the result of Activision’s brilliant marketing machine and its ability to cross-promote its games unlike any other publisher,” Rogers said. “Being able to build on a vast, pre-existing narrative economy allows both existing and new players to quickly find a touchpoint with the game, thereby establishing a different relationship compared to the majority of free-to-play titles currently available on iOS and PC.”

He added, “The persistent rollout of add-ons and expansions cultivates a loyal following and, subsequently, higher earnings.”

While Hearthstone is without a doubt the most successful digital CCG to date, other examples have existed in the space for some time, most notably the video game adaptations of popular CCGs like Magic: The Gathering. Magic’s transition to video games has been somewhat lackluster, however, and many fans have been disappointed in the way games like the Duels of the Planeswalkers series have failed to capture the strategic deck building aspect of the real world card game.

Several other studios have released or plan to release their own digital CCGs, also drawing from existing franchises like Star Wars and Final Fantasy, but they will be hard pressed to approach Hearthstone’s level of success, especially with is massive eSports fanbase.

Screenshot by Eric David