Nintendo fans certainly buy more of them, which I do wonder if third parties consider a problem. Do they consider Sony's first party a problem too, come to think of it?
Of course the statement of 'only buy Nintendo games' may only pertain to AAA games. Wonder if the people who say it would outright say 'Yeah you have 40 Indie games on your system, but you won't buy Mortal Kombat 1, therefore you are the reason AAA doesn't bother with your kind'.
...If Nintendo's large userbase not warranting more focus in development isn't a problem in of itself.
The Democratic Nintendo fan....is that a paradox? I'm fond of one of the more conservative companies in the industry, but I vote Liberally and view myself that way 90% of the time?