Microsoft celebrated Rockstar's Grand Theft Auto IV (PS3, 360) as the top selling title two months running, noting that the Xbox 360 version of the game accounted for 871,000 of the total 1.31M units sold in May. The company added that the Xbox 360 leads competitors in software attach rates, with a "record-breaking" attach rate of 7.7.

Meanwhile, Sony boasted 1.26M software units sold last month, representing a 234% year-over-year increase over last year's figures. The company added that it expects hardware sales momentum to continue in June, propelled by the launch of the PS3-exclusive Kojima Productions' Metal Gear Solid 4: Guns of the Patriots.

"The media have hailed 2008 as the year of the PS3, and with solid sales and growth opportunities ahead, we feel consumers are saying the same," stated Sony Computer Entertainment CEO Jack Tretton.

The Wii's market dominance remained Nintendo's focus in its monthly NPD response. The company noted that its console represented 63% of all current-generation consoles sold in the month of May. Moreover, 19 of the 30 best-selling games in May were made for Nintendo systems, seven of which were in the top ten.

"The diversity of the seven Nintendo games represented in NPD's top 10 for May demonstrates how Nintendo has something for everyone," said Nintendo marketing VP Cammie Dunaway.