On the one hand, it 'only' sold 32.9m units. The PS1 outsold it 3-1. It also had a smaller library. It did outdo the Saturn though.
On the other hand, its biggest games were giant sellers, critically well received and set the standard in their genres. They also started some seriously important franchises such as Smash, Paper Mario and Animal Crossing.
Just wondering what people think. There are certainly other arguments to be made with either choice as well.