Sales of videogames and hardware declined 20% in August, publishers and console makers earning $515.6 million in the U.S. during the month.

Hardware saw the biggest declines, off 39% to $151 million, while new game sales generated nearly $238 million, down 9%, according to research firm NPD Group.

THQ’s “Darksiders II” was the bestselling game of the month, followed by Nintendo’s 3DS version of “New Super Mario Bros. 2” and Square Enix’s “Kingdom Hearts 3D: Dream Drop Distance;” Electronic Arts’ “NCAA Football 13” and Warner Bros. Interactive’s “Lego Batman 2: DC Super Heroes.”

The sale of new hardware and software is said to account for roughly 50% of the total consumer spend on games, NPD said, while used titles and rentals generated $104 million, and digital downloads, including microtransactions, subscriptions, mobile apps and social network games earned $391 million.

While game sales were soft, NPD pointed out that 2012 has seen publishers release fewer titles overall, which is affecting earnings. Most game launches differ from first weekend box office results for movies, with titles showing longer legs given their higher pricepoints.

“What we’re seeing impact August results is the domino effect of the light release schedule from earlier in the year,” NPD’s Anita Frazier said. “That lack of new releases has had a significant impact on subsequent month’s sales.”

As for the console biz, “the current hardware systems are showing their age, so it goes without saying that it would be great to have new systems breathe life into traditional retail industry sales,” Frazier said. “I am anxious to learn more about (Nintendo’s) Wii U launch later this month. And with any luck we will hear news about other systems on the horizon.”

Nintendo’s 3DS XL handheld bowed Aug. 19 and repped 44% of total 3DS unit sales.