Over 20 million Playstation Portables have been sold world wide. Over 40 million Nintendo DSs have been sold world wide. This does not neccessarily make the Playstation Portable a failure, but compared to the Nintendo DS, it certainly isn't a success. However, it has outsold every other portable system not manufactured by Nintendo. Although, it has surpassed Gameboy Micro and Virtual Boys, like many other portables not manufactured by Nintendo, it will probably never surpass sales of the Nintendo DS, Gameboy Advance, Gamboy Color, and Gameboy.
However, will the Playstation Portable increase in the number of sales weekly, or will it decrease in the number of sales weekly? Only time will tell. Because most of the good games that were planned to come out for the Playstation Portable have already come out, the future doesn't look to bright for the Playstation Portable, since its video game library doesn't look like it is going to get any better in the future.
I own a Playstation Portable, as well as a Nintendo DS, and many other handhelds.
The Playstation Portable certainly is not a failure compared to other portables such as the Gizmondo, Nokia N-Gage, Atari Lynx, and even Microvision, but some of the reasons why it has not surpassed Nintendo DS include:
1. Price
2. Lack of first party titles
3. Lack of original franchises
4. Lack of non-ported Playstation 2 games
Although the Playstation Portable has superior graphics to the Nintendo DS, it is slightly bigger than the Nintendo DS Lite, has longer loading times, worse battery, no touch-screen functionality, no microphone, has only one screen (but that one screen is almost just as big as both of Nintendo's dual screens put together). It is just as bright as the Nintendo DS, and its sound quality is debatably just as good.
Because Pokemon Pearl and Diamond have been released, we will see a mighty boost of Nintendo DS sales. The sales for the DS will boost even further when The Legend of Zelda: The Phantom Hourglass comes out, and other good games the future has to offer. I don't think there will be as many, if not at all, strongly anticipated games to come out for the Playstation Portable. But, time will tell.
Other people are looking more negatively towards the Playstation Portable:
I personally enjoy my Playstation Portable. It has one big screen, instead of two smaller screens (yet both screens together almost equal the size of the one, bigger screen of the Playstation Portable (might be bigger, might be smaller)), has great emulating capabilities (another reason why many Playstation Portable games and UMB movies are not selling so strongly) with Atari 2600 games, up to the Playstation Portable. The system looks nice, plays nice, and is very easy to use. It can act as a color camera (Gameboy was able to do this, but was in black and white. I don't know if the Gameboy Advance or Nintendo DS can be used as a camera), play music out loud, without the need of using headphones (unlike the iPod), plays movies, surfs the Internet, and shows photos (the Nintendo DS can do all of that too, but at an extra cost, and with lesser quality (although it is cool being able to use touch screen to surf the Internet on the Nintendo DS).
Every single console and portable has its good points, and bad points, but at the end. Every single console and portable is a marvel of incredible wonder. Even the Magnavox Odyssey is a marvelous machine. However, it is the level of supremecy of each console that determines what console is the better one. No console is "better" than another by fact, but by opinions alone. Just because the Nintendo DS is outselling the Playstation Portable does not mean it is better. It means that it is more successful, but the Playstation Portable contains better hardware. And that is the main reason why Sony is dieing in the video game industry. They are focusing too much on hardware, rather than software, and right now, Sony definitely needs to boost its software if it wants to compete with Nintendo and Microsoft, its winning competitors.
Anyways, the PSP has managed to outsell Nintendo DS at certain points of time:
But unfortunately, it couldn't maintain its limited success:
I personally think that the Playstation Portable is not a failure, but compared to the Nintendo DS, is not a success. Right now, I don't see a Playstation Portable 2, nor do I see a Playstation 4, seeing the direction that Sony is heading. But, there is still hope for Sony. It might not be that big, but hope always exists.
If Sony does fail in the hardware deparment, they are likely to "pull a Sega" and make games for other consoles. I mean, Atari is still making games, just like Sega, so Sony may always be in the video game industry. The only thing that Sony is in danger of, is its hardware department. Sure, the Playstation Portable if the most powerful handheld, and the Playstation 3 is the most powerful console, but if Sony doesn't straighten itself out, it will be forced to only focus on games if its drops out of the hardware department.