Having said that, I found this article on San Andreas' sales very interesting:

In European terms, this figure is likely to be nudging 1.5 million, while US figures could well be in the same ball-park. To sell over three million copies across the world in its first few days on sale would be a truly unprecedented feat for Rockstar, and probably sets a new benchmark for consumer entertainment launches, never mind videogames, with each copy costing consumers an average of UKP 35.45 (according to ChartTrack data).

In gross revenue terms, the game would have generated around UKP 24 million in the UK alone over the weekend, and projected across the world that figure could be as much as UKP 106 million, or put in international currency terms, $195.5 million or 153.97 Euro. Put in context, if a movie were to gross that much at the box office, it would instantly be classed among the all-time greats - that's how big Rockstar's game has become.