Video game players may have been too busy playing with their Christmas toys last month, as U.S. sales of video games fell 5 percent in January. Total sales of game hardware, PC games, console games, and portables fell to $1.16 billion from $1.22 billion a year ago, according to market researcher NPD. And January a year ago was down from the year before that.

The report was expected, since few huge games were released in January. But it will likely be viewed in the milieu of fast growth for casual and mobile games while demand for hardcore games falls. It isn’t the end of the world, but it shows why game publishers have to look to the new digital markets for growth in 2011.

Overall, the report isn’t a surprise since video games as a whole were down 6 percent in 2010. But the game industry has many growing niches, including social network games, mobile games, browser-based online games, used games, game rentals, and free-to-play games on a variety of platforms. We can put out the word that hardcore gamers need to buy more games, but by and large they seem to be doing their part. It’s just not so easy to measure all of the places where video games are growing.

NPD said U.S. retail game hardware sales fell 8 percent to $324.0 million from $353.7 million. Game software fell 5 percent to $576.0 million from $606.8 million a year ago. Accessories were up 6 percent to $235.1 million from $222.8 million a year earlier, largely because of sales of Microsoft’s Kinect motion-sensing accessory for the Xbox 360, as well as Sony’s PlayStation Move wand-like controller.

The No. 1 title on all platforms was Call of Duty Black Ops, the hot-selling combat game from Activision Blizzard which debuted in November. No. 2 was Ubisoft’s Just Dance 2 for the Wii, which has helped revive the dance game category even as the Guitar Hero franchise falls to pieces. Music games aren’t dead; they’ve just shifted to motion-control based dance games from the prop-driven guitar games.

The new titles of the month included No. 3-ranked DeadSpace 2 (pictured) from Electronic Arts, and No. 4-ranked Little Big Planet 2 from Sony. Both of those titles drew strong reviews, but they did not soar to No. 1 as big hits normally might. They were released toward the end of the month, which may explain the light sales for the month in general.