I just want to correct, third best selling handheld. Sheesh people like to act as if there isn't another company with a few fingers on the market.
"iOS gamers on their iPhones, iPod touches and iPads account for a hefty 40.1 million of the estimated 77 million Americans who do mobile gaming. Sony’s PSP accounts for a mere 18 million mobile gamers. Nintendo’s DS family of portable gaming devices account for 41 million gamers (some overlap exists naturally of course). With Apple’s iOS clocking in at less than 1 million less gamers than the Nintendo DS, it has nearly caught up. "
"In European markets, the Nintendo DS family holds a much more comfortable lead over iOS. However, the PSP is behind iOS in the UK, Germany, France, the Netherlands and Belgium."
http://blog.wirelessground.com/apples-ios-passes-sonys-psp/
It is possible that Sony will never catch up.