Batman: Arkham Knight may have had a bit of a rough start, but it looks like its troubles are behind it as the game is reported to have sold over 5 million copies since it launched.

The success that Warner Bros. Interactive Entertainment is enjoying with the game, as well as its other titles, like LEGO Jurassic World and Mortal Kombat X, however, is a stark contrast to the prolonged slump that Warner Bros' film division is experiencing. Given this kind of performance, Warner Bros. Interactive Entertainment is well on its way to earn $1.5 billion in revenue for 2015.

Though just 11 years old, Warner Bros' video game division has beaten more established publishers like Activision and Electronic Arts to take the top spot in terms of sales, taking a 20-percent slice of the domestic market throughout August.

Warner Bros. has a number of gaming hits, Batman: Arkham Knight is one of them, and this has helped offset box-office flops for the studio. Other studios also tried their hand at the video game business, but no one has managed to make it big like Warner Bros.

"We really do feel this year is a culmination of a lot of the investments we have been doing for about a decade," said David Haddad, Warner Bros. video game business head.

It's possible Warner Bros. Interactive Entertainment won't stay at the top of the pack for the remainder of 2015 but it is projected to still have enough revenue equivalent to over 10 percent of the studio's yearly total.

Warner's foray into video games was led by Kevin Tsujihara, now the studio's CEO. However, since he took on the role in 2013, he has been more involved in the studio's movie business, working closely with production, marketing and distribution heads for movies to create momentum for Warner Bros. now that some of its successful franchises have concluded.

Batman: Arkham Knight is the final chapter in the Arkham franchise but Warner Bros. has clarified that it will not be the last involving the Caped Crusader. Batman: Arkham Knight PC will be made available again by the end of October, further boosting sales for Warner Bros. Interactive Entertainment.

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