Yes. This old chestnut. Going off sales data compiled by European chart keepers ChartTrack, it's been revealed that since the launch of GTA IV on April 29, the 360 version of the game has outsold the PS3 version in the United Kingdom. By how much? Well, by around 180,000 copies, with the 360 version moving 750,000 copies, and the PS3 version, 570,000. It's also apparently had an affect on console sales, but since ChartTrack only give out percentages, and not hard numbers, those are useless, and I'm not going to post them. All in all, not a bad rear-guard action by Microsoft's last European stronghold.
360 outselling PS3 since GTA IV launch [Eurogamer]