I think it's safe to say Smash Ultimate is going to outsell Brawl, and be the most selling Switch game alongside Mario Odyssey.

The Wii U was kind of a mess up. It came out just a couple years before the next generation of consoles hit the scene, and at launch there really wasn't much to play. Plus its main controller was the hunky piece of shit GamePad, and once again it was lacking it great 3rd Party Support. Nintendo hit a grand slam with the Switch, but they had to strike out with the Wii U first.