It's interesting how people say Iwata needs to be fired, but it's because of him that Nintendo raked in the profits from 2006-2011 with DS and Wii. And even then, Nintendo turned a profit last year even with a struggling console that is Wii U. I don't think someone should lose their job just because of one mistake in regards to a console. Yeah, the 3DS had its first few months of struggles but Iwata had made sure that it would turn around and doing their new handheld right.
People fail to understand that Nintendo's always had issues with their home consoles since N64. Even when the Wii was a huge success, 3rd parties looked at it to make a quick buck by pushing out shovelware and crap games that don't make use of the Wiimote well. They wanted in on the action even though they have had a dismissive attitude with Wii. When they rolled out the "core" games, it was too little, too late. 2009 is when you saw the big publishers rolling out the core games people had wanted on Wii for a long time. 3 years too late. Those people already moved on to the other competing consoles. And thus, 3rd parties blamed Nintendo when it was Nintendo and the very few 3rd parties making fantastic games and making use of limitations and just creating a great product. You can't have your Cake and your pie.
Wii U is a brilliant concept that unfortunately looks like its life will be cut short. The poor decisions and neglect, not only by 3rd parties but even Nintendo is astonishing. Nintendo royally screwed up with the Wii U (advertising, drought, not rallying 3rd parties as much as they should) and I hope they learn from this here on out. The DS was always the best platform to get your Nintendo games among other great hits and so it made the 3DS a more appealing brand than the Wii did to Wii U.
Again, Iwata should not be fired. I just think he needs to really do some more research and figure out a way to the make their home consoles the best it can be just as they have made their handhelds.
Mario 3D Land did not save the 3DS. It was that and Mario Kart 7 a month after. I think things could have been a bit more different had MK8 released in December for Wii U.