Wii U just has the slightest edge over the Dreamcast for me. I love them both. But my enjoyment of Wii U in its prime was some of my fondest gaming memories.
Dreamcast was always really great too, but it was still fairly evenly matched by what else was available at the time. Every system that gen had incredible games, Dreamcast included.
But the Wii U, in all honesty, felt like it dominated my personal gaming time throughout its lifecycle, even though I had all of its contemporary competitors in my setup. And I know that's a very unpopular opinion. But I feel like it's a tremendously misunderstood console.
Wara Wara Plaza, MiiVerse, the touch screen, etc. They really were going for something unique with their online features that I appreciated. All the system really needed was a MMORPG or RTS to show off why the Gamepad was brilliant. Super Mario Maker and Splatoon got close though.
I still fire up my Wii U fairly regularly even though I have a Switch too. Many games just control better with the Wii remote or the Gamepad like Pikmin 3 or Captain Toad, respectively. It was able to do it all - pointer controls, touchscreen gaming, motion controls, traditional controls, it had its own social media network that was better than mainstream ones for a while, and fantastic 1st party software. Truly a jack of all trades when it came to input devices, but that's also, unfortunately, what diluted its message and concept to consumers.
I really do think that the Switch is a step backwards in so many ways, even though it's a step forward in total due to the portability and joycon versatility. It just can't give as many unique gaming experiences as the Wii U though. Wii U was the most dynamic console we ever got and was a truly worthy follow up to the Wii.
Such a shame that they never really figured out how to market it or launch it with a killer app that showed off the controller properly - Nintendo Land was an excellent minigame compilation, but what they really needed was something like Super Mario Maker, Splatoon, or an MMORPG at launch.