People calling the 3DS a failure is jumping the gun.
Yes, its not selling gangbusters but is still decent considering the price and no big system seller. Now its probably safe to say that the system is selling more on word of mouth than available software, which is probably what Nintendo wanted anyway. The early launch in the year was a smart move, because it allows for them to have plentiful hardware at launch, more time to work on bigger titles for the fall, and use this time as a way to garner third party support. Also more importantly world of mouth will build up to the holiday season where it is more likely that people will spend the yen price tag for this system, and a big title ala Mario Kart or such will be the system seller to gain mass market attention. This holiday will be very big for the 3DS.
The same can be applied to Europe and the Americas. Both regions, have traditionally been slower to adapt to new handhelds compared to the Japanese. Nintendo had to kill the GBA for the DS to take center stage in America. I see this being repeated with the DS and 3DS. The DS is a beast of a system and still sells close to a million units monthly world wide. It will be a while before the 3DS gains the mass market attention, while the hardcore and Nintendo enthusiast will buy the 3DS no matter what. Once again, this early launch will allow word of mouth to spread, and when the holidays approach people will spend the 250 dollars to get the system with the new Mario Kart or similar mass market system seller from Nintendo.
Long story short: Its a 250 dollar system selling with no system seller. Give it time people.