A clearer picture of GTA IV's sales in the U.S. should be available later in the week when the April NPD data is released, but for now Newsweek has obtained sales information from leading video game retailer GameStop, which indicated that Rockstar's blockbuster was sold 64 percent of the time (during launch week) for Microsoft's console – essentially a two to one advantage for Xbox 360 over PS3.

"I think many people have been surprised to see how well GTA IV is selling on Xbox 360 given the history of the franchise [on Sony platforms]. These sales results add GTA IV to a long list of franchises that have switched over from PlayStation to find a new home on Xbox 360 similar to what happened last year with titles like Madden and Guitar Hero," said Aaron Greenberg, Xbox director of product management. "... the majority of third party franchises are being developed first on our platform so they end up playing best on Xbox 360 and when you combine that with Xbox Live, we expect this trend to continue as more multiplatform releases hit the market. With that said, it is fantastic to hear that we beat PS3 two to one on Grand Theft Auto sales from a major retailer like GameStop."

Considering that the Xbox 360 has a much larger installed based – 9.9 million versus 4.1 million PS3s in the U.S. – is that GTA IV ratio really that impressive? PlayStation senior vice president of marketing Peter Dille certainly doesn't think so.

"GameStop probably does a little bit better with the early adopter crowd. There's a larger installed base right now on Xbox 360 than on PS3. So it's not surprising that there's going to be more selling on Xbox 360 than PS3. Having said that, we're really excited about the ratio. If I had an installed base advantage of 3-1, I wouldn't be crowing too much about a 60-40 sales advantage," commented Dille.

He added, "We think it's not as high as what GameStop's telling you, if you look at [the full picture on] the national level. They're outselling us, but not by that same margin, and it's because of their installed base lead. With an installed base lead that's close to 3-1, if you're bragging about a 60-40 software split, it's clear evidence that the PlayStation 3 consumer is overindexing on GTA IV, and the PlayStation brand loyalty that we've been talking about is bearing itself out in the marketplace as we speak."