Monthly US software sales fell 26 per cent year-over-year to $436.99 million, according to July data released by the NPD Group.
Nintendo and Electronic Arts games took the top ten places on the monthly software chart, with Wii Sports Resort debuting at number one.
According to NPD analyst Anita Frazier, Wii Sports Resort has achieved a 2.5 per cent attach rate to the Wii hardware install base.
Combined sales of multiplatform release NCAA Football 10 - the Xbox 360 and PS3 versions took second and third on the chart - made the title the top selling game of the month.
Ever-popular Nintendo franchises like Wii Fit and Mario Kart once again performed strongly, while EA Sports Active and Fight Night Round 4 retained top ten places.
01. Wii Sports Resort (Nintendo, Wii) - 508,200
02. NCAA Football 10 (EA, Xbox 360) - 376,500
03. NCAA Football 10 (EA, PS3) - 237,400
04. Wii Fit (Nintendo, Wii) - 164,300
05. Mario Kart Wii (Nintendo, Wii) - 156,600
06. Mario Kart DS (Nintendo, DS) - 132,200
07. Pokemon: Platinum Version (Nintendo, DS) - 116,400
08. Fight Night Round 4 (EA, Xbox 360) - 116,400
09. New Super Mario Bros. (Nintendo, DS) - 101,800
10. EA Sports Active (EA, Wii) - 96,800