I believe Super Mario 3D World has potential to outperform Super Mario Sunshine. I base my beliefs on;
1. It is a better game than Super Mario Sunshine
2. It has multiplayer funktions, giving it a long term value to consumers that Super Mario Sunshine never had.
3. It appeals to a wider audience than Super Mario Sunshine ever did (the same audience that New Super Mario Bros. appealed to)
It all comes down to how strong Wii U will sell, of course. I believe if Wii U will have to sell 18-20 million systems for Super Mario 3D World to top Super Mario Sunshine.