The WiiU is just the latest in a gradual decrease in Nintendo's appeal to core gamers. Just another nail in a rather large coffin if you will. The lack of third-party support, a failure to recognise market trends over the years and an unwillingness to change is what has lead them to this point.
The damage to their brand can't really be down to a single console, each of the consoles since the SNES have all contributed to an image of Nintendo that has lead to core gamers seeing it as a console only for Nintendo first-party and a general lack of value-for-money.








