The videogames biz is off to a slow start this year, with overall sales down 13% in January to $1.17 billion, according to NPD Group.The largest gamemakers warned of a weak year during their latest rounds of quarterly reports this month. Game sales fell 12% during January from the same period a year ago to $683 million. Nintendo’s “New Super Mario Bros Wii,” which bowed in November, was the bestselling game, with 656,700 units. Electronic Arts’ “Mass Effect 2,” which bowed Jan. 10, was No. 2 with 572,000 copies sold. EA’s “Army of Two: The 40th Two,” and THQ’s “Darksiders” launched softer during the month, with 247,000 and 171,000 units sold, respectively.Sales of Nintendo’s Wii console fell 31% in January, causing overall hardware revenue to drop 21% to $353 million. Sony’s PlayStation 3 moved 35% more units than the previous January, boosted by a price cut late last year. Sales of Microsoft’s Xbox 360 sales rose 7%.