Wii U.
I got one shortly after MK8 launched in May 2014, and after Super Mario Maker in September 2015, the Wii U was even more sad than normal. After that, Minecraft (in December) and BOTW with the launch of Switch were the only notable releases for the rest of the life really.
Pokken, Color Splash, Star Fox Zero and the like were not commercial, mainstream critic, or player favorites.
Wii U feels like the platform Nintendo was putting to bed the earliest. E3 2015 was the point of no return where it was clear the future of Wii U was a low priority for Nintendo compared to 3DS and the upcoming NX. E3 1999 and E3 2004 still promised very exciting futures for N64 and GCN respectively.
N64 had droughts on par with Wii U (at least excluding Wii U digital-only titles) at times, and GameCube was pretty dry in terms of titles in general after 2005, if not early 2005 like you mentioned after RE4.
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 48 million (was 60 million, then 67 million, then 57 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
