But nobody accuses that of being their genre. It has nothing to do with this thread.

Ok let's end this here.

No, let's end it by you taking it out of the OP.

Done.

I really disagree though.

I mean, save for the titles you listed, almost everything has clear genres.

Super Mario - Platformer

Spin-off Marios = Sports/Kart/minigame

Wii series = Fitness/Minigame/Sport/Music

Nintendogs = Sim

Brain Training = Mental challenge

Fire Emblem/Advance Wars = Strategy

Donkey Kong = Platformer

Smash Bros. = Fighter

Wario = Platformer/Minigame

AC = Sim

So almost EVERYTHING has a certain genre (the slashes are for when there are many different games in the series), save for the ones you listed (and even 2 of them were wrong)

I'll just address the title question. Nintendo doesn't feel the need to rigidly stick to genres.

With Metroid, non-prime, it was definitely an Adventure game. In the case of Prime, i would call it an FPS, but that doesn't preclude the adventure portions of the game. FPS is a very broad genre defined by it's name. It's in first person and you shoot things, thus it's an FPS, but that doesn't mean all FPSes are created equal. CounterStrike is not Time Crisis is not Metroid Prime is not TimeSplitters is not Halo, etc.

Not everyone agrees on the criteria for each category/genre

One person can argue that Zelda is an RPG and another can argue it isn't.  What it really boils down to is that their opinions of what an RPG is or should be differ.

Nintendo isn't the only developer with games questioned in this manner, however it is probably one of the most visible ones.

3. Pokemon is called "Pocket Monsters"(ポケットモンスタ) in Japan. Maybe thats why?

Why does every game have to be placed into a genre? I personally like games that have several different types of game play elements. It makes things more interesting. Games like Bioshock which is a FPS action game with RPG elements.