There are two different questions here and people are answering one or the other. First, is "What if the WiiU was from Nintendo's side developed and marketed exactly the same way as today, but was a success?"
The second is "What if Nintendo had made the WiiU into a machine that had a chance of success on the market?"
If the WiiU as it is currently had like 18 million units under its belt, that would mean the gaming market is very different from how it is in reality. It would never happen. People would have to value different things about a product than they do now.
But if the WiiU was changed into a system with lots of success for Nintendo, that would be fantastic and I would enjoy it. There would have been third party games released all through this year! Marketing would have been different. The system itself might have been different.
I'd say as a sales benchmark, the level for WiiU to be considered a success on the modern market is LT at like 35 million evenly distributed throughout the generation. Because that's reasonable market presence to stay relevant in a consumer's mind all generation. But the real decider is profitability.
