Halo was probably the last killer ap launch title ever released and it deserved its success. The Gamecube's launch was poor. Everyone wanted Super Mario 3D GCN but instead we got Luigi's Mansion. That coupled with aggressive marketing(especially in the US), superior hardware, more multiplats, the Gamecube's kiddy design and mostly lack of mature content are only some of the reasons why the OG xbox outsold the GCN.
Super Smash Bros melee. That's above all Mario Sunshine.....
2020 predictions: NSW 25m, PS5 6m, XSX 4.5m, PS4 9m, XB1 3m
In December 2019 i predicted 21m Switch, but that was before COVID, obvius increased my predictions.