I agree with every point you're making there, Goldfish. It seems though that your points about Nintendo holding back Zelda on the Gamecube (which are entirely correct) would, in fact, show that Nintendo themselves agreed with the original statement -

I guess you'd also deny Tetris being system seller for GameBoy back in the early 1990s.

You'd guess right.

The Gameboy situation is actually quite similar - what the system could offer that no other system could is what sold it. People weren't buying it simply so that they could play Tetris. They could do that without forking out for a Gameboy. Just as people could play Zelda without forking out for a Wii.

If you can give me more than a sentence without sarcasm, explain how one non-exclusive game justifies the purchase of a whole new system?

It as an experience justifies the purchase of a new system--- to experience Tetris on the go or to utilize a new control scheme that gives a glimpse at the paradigm change the Wii offers to gaming control.

Exactly. So, taking the Tetris example, what differentiates the experience from getting it on the NES? The "on the go" bit. That is what is selling the system. That is what justifies that purchase.

So, having played Wii Zelda, do you believe the difference in control (your "glimpse at the paradigm change") in that game alone justifies the $250+?

For me, I don't buy a system just for one game anyway.  The idea of 'system-selling', as I see it, is that a game justifies buying the system NOW as opposed to waiting until later.  Had Zelda been a GCN game last year and all things being the same, I most likely would've waited and bought the Wii when Smash Bros Brawl or Mario Galaxy releases; thus making one of those two a system-seller.  Zelda, as a launch title, contributed to me buying the system at launch because it took advantage of the control scheme (and the 16:9 widescreen support).  Owning a GCN and having played Wind Waker on it I knew what to expect there.  I definitely like the Wii controls and prefer it over the GCN controller.

No game... NONE... has ever or will ever justify a price tag of $250+.

You make more sense than most in that respect - I have bought systems on the strength of one game and it hasn't always turned out to be a good idea.

Although, usually the situation is different. There is often a two horse race and someone is going to buy one system and the one that gets that big game first tips the scales. That applies even if those systems are released apart (like 360 vs PS3 or SNES vs Megadrive). In those cases, even though there are hardware differences, both can deliver similar quality games so that 'killer app' becomes all important.

In the case of the Gameboy, DS and now the Wii, Nintendo have put themselves in a position in which the main selling points of their system can't be replicated by the other systems. They're delivering something entirely unique. So the systems, features and promises of games to come can sell themselves. That killer app becomes far less important. It's not like just the prospect of playing Mario64 again sold the DS. The DS features sold the DS.

Those killer apps (Nintendogs for DS, Pokemon and others for GB) came later and just gave a huge boost to what was already a successful system.

You know, as big of a Zelda fan as I am, I would say the killer app of the Wii is still Wii Sports.  I've had about a dozen people who don't normally play games (including my parents, for crying out loud) completely and utterly hooked on the simple fun of playing that.  That is the new experience of the Wii and why I consider it worthwhile.  True, I could've played Zelda on the Gamecube, but I certainly couldn't get "normal" people to come over just to play video games were it not for Wii Sports (or Raving Rabbids, lately... how the heck does the PS2 version of that even work... at ALL?).

In Japan it certainly is as the sales show. In the West though I doubt it would have had the same effect it has now if it weren't bundled with the systems. Here I reckon Zelda sold more systems initially, and Wii Sports' effect will become more visible once there is a slower period with few to no traditional game releases for Wii.