Well, as a Nintendo fanboi, I'm keenly attuned to most Nintendo games. I know the style intimately and it's getting to be old hat. It's no longer the experience of intense, passionate, enjoyment, but rather a more companionate, compassionate, understanding relationship. I've been playing Nintendo games all my life, so on one hand... I'm getting used to them.
*shrug* They're still the best games ever made, no doubt about that.
But for my SECOND reason to not typically be all jazzed up about Nintendo games... seriously, Nintendo doesn't need my help. Their games sell millions anyways. Their stuff is still sitting on the shelves one, two, three years later. I can pick them up anytime, anywhere, anyhow. So even if the game is great, it doesn't warrant me picking it up immediately, just like I don't NEED to read the 7th harry potter book at launch, I'd rather wait until it crosses my path incidentally and naturally.
No, Nintendo is a known quantity, and they don't need my help. But third party games are vivid in their heroic grasping at quality, shocking in their clearly non-Nintendo style, expansive in the range of themes and gameplay they cover that Nintendo doesn't, and provide a more wholesome, more inclusive, and more balanced view of videogames and the industry as a whole.
I made the mistake of buying only Nintendo games for the N64 and GC. Those were the years in which I, personally, exhibited the most close-minded, narrow, hateful, naive, ridiculous tendencies of irrational fandom I can bear to think of. I have made a deliberate choice to not become that person again.