In just eight days, Take-Two Interactive Software's blockbuster Western-themed video game, "Red Dead Redemption 2," has outpaced its predecessor's total sales, Take-Two chief Strauss Zelnick told CNBC on Thursday.

"In eight days, we've sold in 17 million units of 'Red Dead Redemption 2.' That's more than we sold of the first 'Red Dead Redemption' in eight years," Zelnick, chairman and CEO of the Rockstar Games parent, told Jim Cramer in an interview. "Oh, and by the way, the first 'Red Dead Redemption' was a huge hit."

"Red Dead Redemption 2" made headlines last week for its bombastic opening weekend. Take-Two called the $725 million in sales generated by the game "the single-biggest opening weekend in the history of entertainment."

Noting that the game overshot even Take-Two's internal expectations, Zelnick said on "Mad Money" that "Red Dead's" Wild-West-style, action-adventure theme works well in times of extreme social sentiment.

"Westerns seem to find a place at certain times when the populous is feeling a certain way," he told Cramer. "Typically, in really good times, often in really bad times — you can decide what kind of times these are — I will say that I think the sprawling universe that's offered by Take-Two, the extraordinary opportunities to explore that universe and the deep and meaningful story combine with great gameplay to create a great experience."

Take-Two's second-quarter earnings results topped revenue expectations, helped by the release of "Red Dead" and by in-game consumer spending, which Zelnick said was up 28 percent year over year.

Qualms over Take-Two's NBA 2K 2019 game — the next in its widely followed basketball franchise — were overblown, the CEO added, noting that net bookings were up 10 percent year over year and that it was still the "biggest-selling sports game" for 2018.

Shares of Take-Two fell 5.3 percent intraday on Thursday, sliding further in extended trading.