Pokemon Stadium hands down for me. I was so psyched to play a full on 3D pokemon game and what we got was little more than a pokemon 3D play set.
Dishonorable mentions:
Paper Mario Sticker Star (so boring and hardly an rpg)
Xenoblade Chronicles X (love the first and am loving the sequel on switch. But X felt so aimless it never pulled me in
Bonus: i absolutely love Star Fox Zero. To me its one of the best Wii U games, my favorite Star Fox, and one of the best motion games out there. I do not understand why the controls were so complex for folks (granted takes getting used to)
And metroid other M...is more so bad because its a Metroid game and its legacy towers over it like a child with a magnifying glass towering over an ant pile.