Of course the sales were real, but I think the argument people make when they discount it as an outlier or anomaly is that it didn't create anything for Nintendo to build off of. It' didn't create a loyal fanbase they could sell more hardware too. It was monstrously successful for a solid 3-4 year period, and moved tons of hardware and software, but when people dropped it they dropped it like a rock and the brand meant nothing to them.
I know that lots of people like to hand-wave that by saying "well of course people dropped it. Dem casuals right? lololol"
I do not believe that is correct. I place the blame on Nintendo, actually, for failing to pursue that audience more aggressively by giving them more of the games they wanted. After NSMB Wii, Nintendo's efforts on the system were decidedly Gamecube-esque, which is the opposite of what the Wii audience wanted.
Let me frame it this way: why was there a Super Mario Galaxy 2 but no NSMB Wii 2 or Mario Kart Wii 2? Why was Skyward Sword single player and kind of "advanced"? I know some of these questions sound crazy, but strictly speaking from a business perspective, Nintendo started making the "wrong" games mid-way through the Wii's life which tracks pretty neatly with the decline in popularity and sales. The games coming out did not build on the promise of motion controls for the audience that had bought the system for Mario Kart, Wii Fit, and Sports.
And where are they now? And how many closets did this thing end up in or collecting dust after that novelty worn off? I am not discounting the sales at all, just pointing to why it is now seen as an anomaly for them.
As stated above, it is my opinion that it was Nintendo's fault. They did a terrible job of serving that audience post-2009 (when NSMB Wii and Sports Resort launched).
It came out at the right time, a more impulsive price with a motion control fad that cashed in on the grannies and soccer moms who were loving the touch games on their iPhones that started to boom at the same time.
The notion that it was an "impulse buy" and a "fad" is objectively false.
If it was an "impulse buy" then why did people wait weeks or even months to get one? Why did sales remain absurdly high for the first 4 years of the system's life? At that time of the Wii's life, I worked retail. I have first-hand experience of dozens of people calling every day and stopping in the store each day asking if we had a Wii, and this was mid 2007, a year after the thing launched.
A fad? Maybe, depending on how you stretch the word, but definitely a longer-burning fad compared to a lot of other gaming stuff.
Not saying it was bad, I loved some of the Nintendo games on mine. But as a more core gamer than the mass who bought it, that waggle effect wore off in a month and I was playing games on a classic pad.
There are other people with similar experience. On the whole, however, the numbers don't lie. A lot of people bought the system and on average they bought 9 games. Without more granular numbers, I can't say if those game purchases were frontloaded (I doubt it) but at least we can infer that most people didn't buy the system for Wii Sports, get bored, and then tossed it in a closet.
It was an anomaly for them for system sales, because as I said before, their systems have been on a 10 mil on average decline every year. And Wii removed, it is followed that exact pattern to a T.
In that sense, we are in agreement. I think the steady decline is due to Nintendo focusing on their core audience and not reaching out to new customers. Wii (and DS) were all about reaching out to new customers, which is why those two platforms are the two most-successful platforms in the company's history.