This is a tough thing to quantify. But if you’re looking for the intersection of great software and lousy sales, I can’t think of a more worthy system than WiiU.
I understand WiiU suffered from poor marketing, game droughts, and a clumsy controller, but it still boggles my mind that a system with Mario Kart 8, Super Mario 3D World, Bayonetta 2, Pikmin 3, Tropical Freeze, Splatoon, Super Mario Maker, Smash Bros., and Xenoblade sold only 13.5 million.
Dreamcast and Saturn would be right there as well.