the definition of peripheral is largely debateable.
The wii mote is not a part of the core system. A keyboard is considered to be a peripheral, why shouldn't a controller be?

In that case, you're still wrong. The SNES controller was obviously the inspiration for the PS1 and PS2 [edit: and PS3] controllers, so it has [edit:  more than] 300 million consoles it can lay claim to.

And to answer your question, because it comes standard with the console. Is a keyboard really a peripheral for PCs?  [edit:  And even if it is, I wager it's because PCs are built, so "peripheral" could reasonably refer to anything you don't put inside the case.  For consoles that would be a useless distinction.]

[edit2:  Or, if you reject the SNES argument, you still cannot reasonably deny that the PS1 and PS2's controllers are identical, for almost 250 million combined.  Or for that matter EACH of the PS1 and PS2 sold more than the Wii has yet, as did the NES (for the moment), making your claim ludicrously false.] 

Sometimes I tend not to read the quote and I'm used to read full words not abbreviations.

why do people keep bringing up Nintendo's third party problem?

third parties will never support Nintendo's consoles seriously because Nintendo is a very tough software competitor. they're the largest game publisher, what do you expect?

third parties release their games on other consoles because they have higher chances at succeeding there.

@final fan
lol you're too much
Isn't the wii outselling everything at a faster rate? Wouldn't that make it the most accepted? whatever, this is such a stupid argument.

As far as the peripheral topic is concerned, a video card can also be called a peripheral.

Why do you need to be right about something so trivial? You want me to recant my statement? Fine. The wiimote is one of the best designed peripherals (controllers) of all time.

Wait, wait.  What, by your definition, would NOT be a peripheral?  I honestly am curious.  [Wikipedia agrees about keyboards in computers, so it's a fair analogy.]

As for "most accepted", wouldn't the most sensible measure be the amount of the gaming community that is accepting it?  The NES wins by far in that case, right?  (The Wii certainly doesn't.) 

And now you're talking about "best-designed", which, although I agree, is a very different thing.   

I disagree that it's trivial at all.  But if your modified statement is indeed your true position, then we do not disagree on that.  Except, perhaps, for the correct usage of a certain word.   

Not to beat a dead horse, but the Wii Remote in fact is one of the most REJECTED controllers. How many people have you heard screaming about waggle? It's garnered more scorn (however undeserved) than the Duke Xbox controller ever did.

a peripheral is anything that is not needed for the core to function. A wii can function without a wiimote. It will be limited but it can function.

A power supply is not a peripheral.
A mobo/processor/ram are not peripherals
some kind of internal memory at least is required, so a hard drive could be a peripheral.
Video processing can be done right on the mobo, so a standalone vid card is a peripheral. Additionally, a computer can run without a video card, it just cannot display images, and not all computers require that either.

an optical drive is one
video card
Hard drive
input
speakers
communications

a good synonym for peripheral is supplemental, as in something that acts as a booster, or something that facilitates existing abilities.

At least that's my take on it.

Well, the "core function" of the Wii (or any game console) is for people to play games, which I argue would be pretty difficult without a controller.  But I've already edited my post regarding that issue.  As for the rest...

One: they're going to compete against Nintendo regardless.  Putting games on non-Nintendo consoles just means they're competing indirectly because Nintendo consoles compete against the non-Nintendo consoles; Nintendo's games boost Nintendo's consoles against rival consoles, which includes games on those consoles.

Two: even on other consoles, it's not like the pie is shared equally by third party games; games on the HD consoles have to compete with the likes of Grand Theft Auto, Final Fantasy, and Call of Duty (which is also on Wii, but clearly favours the HD side).  That third parties are on average more successful on other hardware has more to do with these behemoths being largely focused on non-Nintendo systems, which skews the numbers.