Let's see here....
Xbox Live
Halo
Some multiplats that the GameCube didn't get (Star Wars: Battlefront, GTA, etc)
I really don't think anything more needs to be said on why the Xbox won.
The GameCube WAS beating the Xbox until late 2004. I bet we all know why the Xbox moved past the GameCube at that time.
Lifetime Sales Predictions
Switch: 151 million (was 73, then 96, then 113 million, then 125 million, then 144 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 57 million (was 60 million, then 67 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