Even the mighty video game industry had trouble keeping up in 2009, as overall software sales in the US, UK and Japan – its largest markets – saw an 8% dip last year.

The data comes from Top Global Markets, an integrated monthly report from The NPD Group, GfK Chart-Track Limited and Enterbrain. The 2% decline of software unit sales in Japan was softer when compared to the US and UK, which saw respective decreases of 7% and 14%.

NPD industry analyst Anita Frazier notes that year-over-year comparisons show declines, but the industry is still moving significant volumes unseen before 2008. She says that because of the large investment needed to produce software for the latest set of consoles, several publishers are talking about releasing fewer titles each year to allow their teams to focus on maximizing the success of each title. But the year-end data shows the number of titles entering the market is still growing (778 new titles in 2009, up from 764 in 2008).

Nintendo Wii games dominate the top-five video game titles, but they couldn’t nudge the popular Call of Duty: Modern Warfare 2, which sold 11.86 million units at US retail, from the top spot. It was followed by Wii Sports Resort (7.57 million, US), New Super Mario Bros. Wii (7.41 million, US), Wii Fit Plus (5.80 million) and Wii Fit (5.44 million).