Hmmmm...I don't know if I can agree with that.
The N64 was a complete failure in Japan (only selling around 5 million units; a huge drop off from the SNES's 17 million), it never managed to gain back any ground that the Genesis had stolen from the NES or improve on the NES's NA numbers despite being more western focused (The SNES and N64's NA LTD is around a stagnant 20 mill while the NES was around 34 million), and it failed to stop the new-comer console from completely dominating it. I feel that you kind of have to do a bit of stretching to make the N64 sound like a successful console in any area that doesn't involve software.
The NGC...well...do we really need to debate on that? Iwata has pretty much flat out admitted that it was a failure in almost every respect, and he never wanted to see the company in that position again.
:/
If we consider N64 and GC failures, then we have to consider every home console after the 16-Bit Era and before the seventh generation was a failure besides the PS1 and PS2... Actually, considering the dominance of the Atari 2600 in the second generation, the NES in the third generation, and the assumed dominance of the PS4 in the eighth generation, it looks like having two or more competitive home consoles in a single generation like the SNES & Genesis or the Wii, PS3 & 360 are aberrations compared to the eras when a single console is completely dominant like the Atari 2600, NES, PS1, PS2, and likely PS4.