1. My point here was just that, Wii drop after 5-6th year was like nothing compared before, not even like N64 or GC, and definitively not like a console like SNES. According to that super interesting graph on Nintendo shipments (thanks for the info) SNES shipped 1'8M in Japan, 2'9M in USA and 800k in others, so around 5'5M total in its 6th year. SNES best year was its 3rd with 4'1M in Japan, 5'6M in USA and 2'4M in others for a total of 12'1M that year. That's basically around a 45% compared. Wii in its 3rd year summed 26M compared to 9'9M in its 6th year (based on the same graph) so around 38% compared to that year. That's already a huge difference, but SNES still sold fairly fine another 4 years more in NA, while Wii stopped production a year later worldwide. That's what i was comparing. NES, SNES, DS,... did indeed lasted way longer than Wii.
And yes, software for Wii after 2010 was horrendous indeed, but that's not a point in favor to Wii....That's why it sold so poorly in later years. The lack of the same 3rd party support Wii received its first years compared after year 5 or 6 is a clear hint of what the consumers tendecies were at the time.
2. My bad in expressing myself badly with this point. What i was trying to say is that N64 was basically replicating the success of the previous console during the first years and ended selling 67% of what SNES sold (because for whaterver reason, Japan didn't bought N64 consoles like with SNES). If it wasn't for the japanese market, N64 would've been similar in sales to SNES, so my point was that in the west N64 was not a failed console, it just looked bad compared to what Sony was doing with PS1. So, despite being beat by PS1 worldwide , its successor, Gamecube, still sold 22M next gen and most new franchises starting on N64 like Smash Bros, Mario Party or Animal Crossing grew a lot during that gen, even if the console itself sold less than N64. That wasn't the case with WiiU compared to Wii. WiiU sold almost a 1/10 of their predecessor and no franchise went to be considered better or sell better on WiiU. In respect of your use of PS2 and PS3, It benefits my point in fact. Both WiiU and PS3 had problems with its concept from the beginning but the PS3 ended selling way more than WiiU. My opinion on why??, loyal consumers satisfied with PS2 wanted more PS consoles, than Wii consumers wanted more Wii branded consoles. PS2 left a legacy for PS3 in the end in a way Wii wasn't capable for WiiU. Like you said, Wii last few years were awful software wise and it reflected in declining sales for Wii and lack of support from the masses for WiiU.
In conclussion, Nintendo home consoles, despite their succesful software sales have always been found difficulties to sell more than 50M, being Wii an aberration in the high end and WiiU in the low end. That's why Nintendo decided to go the Switch route (and why is working so good too).
I snipped points 3-5 because I don't think that the discussion can go any further with them.
1. Looks like you rushed the numbers. Here are the same comparisons between the third and sixth fiscal year for other home consoles.
N64 - 7.9m, 500k - ~7%
GC - 5m, 700k - 14%
Wii U - The link doesn't show Wii U numbers, but we know the percentage is 0% because Wii U didn't ship any units in its sixth fiscal year.
The NES doesn't have individual numbers for its first three fiscal years in Japan and the launches in America and Europe were staggered between individual states and countries, so a proper like-for-like comparison is not possible. The DS's value exceeds 100%, but that's not the norm for consoles.
What you call a huge difference between the SNES and Wii is among the closest values you get in this kind of comparison. Personally, I don't consider such a comparison valuable due to the involved variables, but going along with your suggestion reveals that your conclusion is wrong. The Wii is most similar to the SNES; other consoles show significant differences to the Wii.
Wii's third party support has first and foremost to do with the contempt that third parties held for the console. They usually didn't want to develop quality titles, but were rather looking to cash in with quickly made games. Since consumers stopped buying the low quality games while third parties didn't want to make quality games, third party support was scaled back a lot. Consumers were definitely interested in playing Wii games, because Nintendo games sold well throughout the Wii's life. But even for Nintendo support it looked lackluster from 2011 onwards, because the 3DS launched in early 2011 and demanded Nintendo's attention, even moreso when it struggled.
Overall, it's misguided to conclude that the Wii's decline is due to a reason like fad or unwillingness by consumers to buy more, because the situation of the software pipeline provides the more logical reason that the sharply declining number of interesting game releases resulted in the declining hardware and software sales.
2. Point 3 in my previous post addressed this already. You are of the opinion that consumers should buy a brand, but I explained that Wii and Wii U aren't similar consoles despite both using the same brand.
I don't think it makes sense to put much stock into the late life support of a console and how that translates consumer confidence in a new console. The Wii U's software pipeline was woeful from start to finish and awfully bad in 2016, but none of that harmed Switch. The Wii U failed because of what it was, not because consumers were supposedly very dissatisfied with the Wii.
Nintendo decided on the Switch route in late 2013/early 2014 because both the 3DS and Wii U had run into extended software droughts due to rising development times for games. Under such circumstances it would be incredibly difficult to adequately support two separate Nintendo consoles with first party software, that's why Nintendo looked into ways to solve this problem. The other big factor is of competitive nature because at that point in time it was already clear that Sony was going to exit the handheld market; that would have left Nintendo as the only console manufacturer to support two consoles if they had continued with the same strategy. It was a decision that was equally motivated by the circumstances of the home and handheld market, because Nintendo wasn't satisfied with 3DS sales either.