Last year was truly a great year for video game sales and 2008 is not showing signs of this trend stopping anytime soon, with the industry reportedly on pace to see revenue in the $21 billion to $23 billion range this year. According to NPD’s latest report, US sales of video game hardware and software were $1.12 billion in May, up 37 percent from a year earlier.

There’s not much to be surprised about in NPD’s latest report. Sony’s PlayStation 3 once again outsold the Xbox 360 with 208,700 units moved compared to 187,000 for the 360. As usual, the DS and Wii took the lead on hardware sales with 452,600 and 675,100 units sold respectively, but this time Nintendo also ruled the software charts with seven of the top ten best-selling games in May being on either the Wii or DS – something that’s rather unusual.

Nintendo game sales were led by Mario Kart Wii, which was just behind GTA IV in second with 787,400 units sold, and followed by Wii Fit which sold 687,700 units despite supposedly being supply-constrained in the US. Check out the rest of the numbers here.