I guess people are more quick to jump into the "Nintendo is dead" bandwagon because they basically only sell consoles. Let's face it, if the X1 had sold zero units and MS had millions of unsold inventory it would still barely scratch their financial report. They have much more room to underperform before having to quit consoles. Also, notice that I said "quit". Nintendo and Sony would pretty much go bankrupt in the same scenario. In a similar way, people also were quick to consider Sony done after the PS3 and it could even be the case if they tried to be stupid this gen instead of hitting a home run.
Also, Nintendo has the most fragile position. MS has infinite cash, Sony has a global leadership and is usually way less prone to screw up their products (their worst shot at home console sold 80M). Nintendo has a strong position with handhelds but, unlike home consoles, they are suffering with the competition of mobile devices. Also, comparing the sales of 3DS and other consoles is pretty much ridiculous when the 3DS basically was 170 bucks 6 months after launch and reached as low as 100 bucks. The PS4 and X1 are basically 2 times more expensive now than 3DS was in 2012.