The Wii had a ton of great games outside of the Nintendo specific ones. The Conduit 1 and 2, Golden Eye, tons of fighting games, it gave us No More Heroes. The Force Unleashed somewhat had the best edition on the Wii (this is mostly subjective but it's a strong consensus that the Wii's version held up). Its main appeal to other consoles I think was how diverse the games could try to be - silly games like Boom Blox and De Blob, and niche ones like Endless Ocean for all the marine biologist kids.

Granted, I grew up with some of these games and I'm not trying to say that the Wii's extensive library is all stellar. But there are many gems amongst it. The Wii's popularity drew a lot of attention to games that would just be scrolled past as shovelware on other online stores (Xbox Live mostly). Few of these were outside of the Xbox Arcade or whatever it was, but on the Wii they would be digital and sometimes have physical editions. Also because of how wide its demographic, it had a few surprisingly decent Barbie-esque and Horse care games. I mean, it had so many games made for it that only just stopped getting games in 2020.

The Wii U was an attempt to bridge the gap between the success of their portable line, the DS, and the Wii. Growing up all any kind ever wanted was getting their consoles connected. But then when the Wii U finally came out and was marketed, its main selling point was that you could play your game on the tablet while someone else was using the family TV. I mean really, it was exactly what every 10-14 year old into Nintendo was talking about up until Nintendo actually made it.

Part of it was marketing, I remember a lot of people being surprised that the gamepad wasn't what was being sold, but a whole console with it.

It's crazy that it failed honestly but at the same time it's totally understandable. You can't try to be both a home console and a "portable one" when what's portable is connected to the Wii 2. It was the genetic imprint that wanted to be everything the Switch became.