The game industry as a whole amassed $1.12 billion across the month, marking a 37% leap over last year's May figures. Despite its $90 price point, Nintendo's Wii Fit sold 687,700 units and clocked in as the month's third best-selling game.

For the first time since its November 2007 debut, Infinity Ward's Call of Duty 4: Modern Warfare failed to place among the month's ten best-selling titles.

May hardware sales in the United States were as follows:

1. Wii - 675,100 units
2. Nintendo DS - 452,600 units
3. PlayStation 3 - 208,700 units
4. Xbox 360 - 186,600 units
5. PSP - 182,300 units

Meanwhile, May's best-selling console games in the U.S. were:

1. Grand Theft Auto IV (Rockstar, X360) - 871,300 units
2. Mario Kart Wii (Nintendo, Wii) - 787,400 units
3. Wit Fit (Nintendo, Wii) - 687,700 units
4. Grand Theft Auto IV (Rockstar, PS3) - 442,900 units
5. Wii Play (Nintendo, Wii) - 294,600 units
6. Super Smash Bros. Brawl (Nintendo, Wii) - 171,100 units
7. Iron Man (Sega and A2M, PS2) - 130,600 units
8. Guitar Hero III: Legends of Rock (Vicarious Visions, Wii) - 116,800 units
9. Pokemon Mystery Dungeon: Explorers of Darkness (Chunsoft, NDS) - 107,000
10. Pokemon Mystery Dungeon: Explorers of Time (Chunsoft, NDS) - 102,000 units

Frazier went on to note that sales of Rockstar's Grand Theft Auto IV have reached a combined sales total of 4.2 million units, making it the year's top-selling game so far.

"Coming in at number 12 on the top-sellers list, We Ski from Namco, which utilizes the Wii Fit balance board, was able to capitalize on Wii Fit's cross-promotions in circulars and at retail," Frazier added.

NPD also reported that year-to-date sales of Guitar Hero III and Harmonix's Rock Band have reached 2.5 million units 1.3 million units respectively, earning both games a place in the year's top selling titles.