2011 and 2012 give 2015 and 2016 a run for their money though. While the game output was better during those years, the Nintendo behind the scenes was much worse. In 2011 the 3DS had extended software droughts and after the price cut and a recovery, a Nintendo representative came out to state that the 3DS taught them software sells hardware. As if that is a lesson that should have ever been in doubt, but Nintendo really believed that 3D will sell the 3DS on its own. Everything concerning the Wii U in 2011 and 2012 spelled upcoming disaster.
I terms of the 3DS, I'd say Nintendo also made the mistake of assuming third parties and developers will blindly trust them with the 3DS because of its predecessor's pedigree, so they decided to cut corners on Launch titles, so that third parties can take the spotlight. But when it became apparent that third parties didn't have much ready either due to them still supporting the DS, the bigger titles not being ready yet, or skepticism of the system versus the PlayStation Vita, Nintendo scrambled to try and clean up the mess they created with their naive assumption. I once heard that Retro Studios was only brought in for Mario Kart 7 just to get the game out in time for the Holiday season.
This mistake would be repeated with the Wii U as Nintendo just assumed the Wii's brand recognition, and increased power would mean the third parties would just crawl to their side en mass. But when the reality of the Wii U became apparent, Nintendo was caught with their pants down, and lost a ton of money on just trying to keep the system afloat as Third parties began packing their bags for the real next gen consoles.