Hiroshi Yamauchi was the man who was behind everything good at Nintendo. Everything good that happened in the company was his doing, all the bad was also on his watch.
That bad that includes the Gamecube, the console that almost killed the company.
In Nintendo's darkest times Yamauchi was the one who steered the company in the direction of the DS which in his words saved the company. He also laid plans for the Wii.
Yamauchi stepped down and passed the DS and Wii to Iwata. Even Iwata's incompetence couldn't destroy the DS and it took years of abuse for the Wii to finally die in 2008.
Without Yamauchi's forward thinking Nintendo has been a shell of it's former self.
You have the 3DS which is a failure. Iwata had to reduce the price of the hardware by one third to get traction and even now it fails to bring in the software like Yamauchi's DS did.
The Wii U is failing and only gets worse every month. It's literally more money than it's worth for Nintendo.
Sadly Yamauchi died this year so there's no savior coming for Nintendo anytime soon. He was the only one at the company that had the vision to not only know what would work going forward but was also agile enough to fix problems without damaging the company.
Iwata is a problem, his bastardizations of Yamauchi's DS and Wii fail to perform and there's no help in sight to the point where Nintendo is bringing back the DS design with the 2DS.
So much praise is heaped on Miyamoto for his ability to innovate but it was Yamauchi that put him in that position to succeed. Under Iwata's leadership Miyamoto has been relegated to a bit player at Nintendo.
Yamauchi's long history with the company allowed him to see trends coming and going. Nintendo was never friendly toward third party devs under his watch but he was able to make the singular focus work.
No one currently at Nintendo thinks like Yamauchi and that's a very big problem for Nintendo going forward.