I don't see why not. Some of my best friends who are Nintendo enthusiasts are hardcore gamers. It also depends on how you look at 'Nintendo gamer". I know people who use the Wii exclusively but don't buy games like Mario or Zelda, so to me It would depend on the kind of Nintendo games that person plays since Nintendo's umbrella is rather wide. But I suppose technically those guys wouldn't be seen as 'Nintendo gamers'.
Playstation = The Beast from the East
Sony + Nintendo = WIN! PS3 + PSV + PS4 + Wii U + 3DS