It's pretty silly that people can consider the PSP anything but a success. No other non-Nintendo handheld ever came close to sniffing the numbers that the PSP has put up. Software sales aren't very good relative to compeitition, but it still has 50 million sellers with several games that within tens of thousands.
If you told someone in 2005 that the PSP was going to have over 75 million lifetime sales, they would have laughed in your face.