You have to wait until the new consoles start selling, then you will know whether it is a failure or not. The PS360 already have their momentum going, they are cheaper, have a huge library of blockbusters titles, etc so it isn't fait to compare the Wii U with these two and then calling it a failure simply because the fact that it is new or next gen (which is another thread all on its own) is not a bit enough selling point to beat the current gen consoles.
To answer your question, the Wii U is not a failure. It still has a way to grow but it does look like the public's interest for the Wii U is stagnant.