^That's rather stereotypical, actually.
Most of the time it's because Sony/Xbox fanboys think that Nintendo games are too "kiddie", hence they bring up CoD, a "man's game", in their arguments. But then again, they're thinking of Mario, Pokémon and Kirby (though the latter is very questionable, eh Zero/02/Drawcia Soul?). What's funny is that these "kiddie games" have more story and plot than most of these "manly games". Also, the fanboys seem to ignore the many other Nintendo franchises, including the following:
-Metroid
-The Legend of Zelda
-Earthbound/Mother (though I guess it's excusable, given its obscurity)
-F-Zero
-Super Smash Bros.
I guess it's because Nintendo games are colourful and bright, instead of being dark, dull and in sepia tone. Ah well.