Best is tricky.
2010 and 2022 are tied for the most games I've ever bought for a single system in a single year; (on Wii/Switch respectively) I was practically snowed under with great stuff to play and it was awesome. 2017 and 2023 also deserve a mention for packing in a ton of top tier first party content.
Weakest has gotta go to 2016, the Wii U's final year was embarrassing.







