In addition to what others have said, a large part of the problem here was that the marketing heavily focused on the GamePad rather than showing the whole console. So it was an understandable mistake to think the Wii U was a controller. That's not a problem any of those other systems had, they were more clearly advertised as consoles.

Super, Color, Advance all describe the console. The customer knows what they are getting.

U is a letter that gives no information. Is it a themed Wii for college kids? Is it a U shaped controller upgrade? Is it a screen addon? Is it an online social media thing?

If you had asked me before coming into this thread what the Wii U actually was, I wouldn't have been able to tell you. I knew it was a flop. I knew nobody who actually had one. I didn't even remember it had a screen. I knew I wasn't interested in getting one at the time even though I had a Wii and a 360 but didn't have either the PS4 or XBOne. So I think both the weird name and the fact it wasn't wanted or needed by anyone are to blame for its failure.

To me Super Nintendo sounds like a super version of the Nintendo, and Super is the first word.

Game Boy Color implies it is a Gemeboy with a color screen.

Game Boy Advance sounds like an advanced version of the Game Boy.

Wii U tells you nothing. It starts with Wii and then adds the nonsensical letter U, that's all the information the name conveys.

Basically way larger audience. The big thing in gaming around 2005-ish is that everyone is a potential gamer, including people who mostly don't care about or are not used to specific console releases.

Also I'd argue a "Super" is a clearer mark of upgrade than a single, very random letter or number (that is specifically not used like a version number like "GameMachine 4" but instead a weird portmanteau).

Also counterpoint : Nintendo of America used a lot of marketing to try and make people stop calling consoles "a Nintendo", and part of this was the lack of distinction between NES and SNES (the other part was confusion with the competition).

3DS was a new system and significantly more powerful than DS.

You can see it mostly on what 3D games on DS look like in comparison, they were generally very limited. Of course 3DS had a rather low resolution (though already higher than DS), but it could do a lot more. Roughly, imagine going from N64 to Gamecube or Wii visually.

3DS also had a few specific abilities, obviously stereoscopic 3D, but also an analog stick (of sort, but still making a huge difference), console to console passive communication (street pass), NFC reader, and motion sensing (surprisingly great for aiming, made shooting in Zelda games a breeze).

3DS actually had its own new model with the "new 3DS" (that name.... they never learn).

This one was mostly the same but more convenient. A lot more stable 3D, especially if you're combining it with motion which was basically impossible before, a second (rather shit) analog stick, a second pair of triggers. You could have these new inputs on a standard 3DS through an accessory, so they just integrated them.

New 3DS was also more powerful, but a game needed to be specifically made or updated for the n3DS to access that extra power. Very few games were updated, and even fewer were exclusive to new, only notable one probably being Xenoblade Chronicles.