In an attempt to better explain why Wii won but still lost (won due to previous measures, but lost in gaming culture), I made this graph to show the trunk structure of console gaming culture. The mainline (or trunk) is usually holds the winner of the previous generation and note that usually if a parent console is extremely popular the successor will be popular as well. Where does this concept diverge? Generation 5 and Generation 7.
In Generation 4, gamers were presented with an evolution from NES and as such they choose SNES, however Genesis did well too, why? Because the content for SNES and Genesis was similar. Looking at Gen 5, gamers were presented with a revolution. Games on all systems were not very similar (with Saturn and Playstation being the most similar, but not enough). Games were not similar to each other OR to the previous generation of games. This presented a dilemma to gamers and an opportunity to define the destiny of future gaming culture. They chose Playstation.
In Gen 6, PS2 was very similar to the previous generation, while the competition tried to remain dissimilar. This proved unsuccessful as the trend continued and anyone that did not mimic the trend of PS2 content lost (Xbox tried to mimic it, but not enough).
In Gen 7 something interesting happened, you have 2 consoles that were extremely similar (the 360 and the PS3), and something completely different the Wii. If previous gaming culture behavior were to predict the outcome, the sales winner (the Wii) would have dominated Gen 8 and become the new main trunk of gaming culture. Obviously this did not happen the successor to the extremely popular Wii, the Wii U, has apparently failed to become popular despite no competition in the same generation.
The question is why? The answer - PS3 and 360 were so similiar that their shared content became the new trunk. In Gen 8 this trend will continue as long as the Xbox One has a sufficient amount of similiar content to the PS4 and visa versa.
So this leaves Nintendo with two options in the console space.
1. Be unique and have the gaming culture adopt you as the main trunk of gaming culture. This did not happen with the Wii apparently, despite the sales. So in order to accomplish this Nintendo needs a new system that was more popular than the Wii.
2. Be similar enough to the Sony/Microsoft console that developers make the same games for the Nintendo system.
To give a better answer to the person who contested my "feel" of Wii being a failed console. Look at the graph, all system not on the main trunk of any given generation are especially unique with respect to the main trunk. This uniqueness is what makes them popular with some people. Dreamcast and N64 and GameCube for some people are beloved, but it also makes them a console that failed to become adopted to the main trunk (which is part of the main console gaming culture). Wii has that same feel of uniqueness, great unique content feel, that was not at all adopted by the main trunk. Sure Sony and Microsoft did their own motion controls but they had no staying power and eventually become very unpopular.