I knew the DS is king (or should I say queen?) in the UK, but the PSP is really in a state of decline. I don't see anything that's going to change the situation either.
http://www.pocketgamer.co.uk/r/Various/PSP+Slim+&+Lite/news.asp?c=10822
A total of 4.1 million PSP games were sold in 2008, compared to 5.6 million during 2007; a decline of 27 per cent. Indeed, the value of those sales dropped slightly more, from £111 million in 2007 to £70 million in 2008; down a rather staggering 36 per cent.
A total of 19.1 million DS games were sold in 2008, up 28 per cent on 2007's total. In terms of revenue, in 2008 the DS software market was worth £366 million, up 17 per cent compared to 2007.