The success of the Wii was due to mass market appeal, though it left Nintendo's original fanbase wanting up until about four years ago with the announcement of the 3ds. Full disclosure: the 3ds and most games on it revived my hope with Nintendo.
I own the three major consoles right now and the only one I feel like I've wasted my money on is the Wii U. Just speaking for the console itself, without considering the poor game availability, it is far slower and using the online features is significantly more tedious. I routinely clock 5-20 seconds more than the competition to load different menus.
I actually do see the point of the gamepad, though its battery life is piss poor. I enjoy using it, but I can't help but feel as though games don't need to be using it to make for a good gameplay experience. The two screens on the 3ds are great, sure, but a game on a big screen has more than enough room to display all the information.
I'm fairly open minded to games, but since I rule out most of Nintendo's samey Mario platformers (color me cynical but after 20+ years, I'm bored of Mario), I have only 2 games on the console that appeal to me. This is juxtaposed to the 25+ games I have on the N64, or the 20+ games I have for the SNES, or the 15+ games I have for the GC/XB360/PS3/PS2. We'll leave my steam directory out of this one. Suffice to say, I've bought a console that barely has games I enjoy playing based on the success of previous Nintendo systems.
Why should someone invest this when they could have spent $300 on games for another console? Games that deliver? I don't mind that some people enjoy these repetitive Mario platformers, per say. I don't mind that people enjoy Mario Kart. I mind that to play these games I have to pay the same price I'd pay for a much higher quality game on another console with more total hours of playtime. With the Wii it was different, since the games and console were significantly cheaper. This is not the case with the Wii U and yet the Wii U charges about the same as the competition (especially when you factor in those Amiibos). It feels like Nintendo is trying to take my money from me rather than inspire me to buy from them and everyone is okay with this except me.
I'll just say this: with the 3DS and the announcement of Zelda U I was rooting hardcore for Nintendo and felt like they were finally back in the game. This E3 left me sorely disappointed as a fan.