Wii has a fantastic 3rd party game library

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Mummelmann said:
The Wii's massive decline started long before the Wii U was even announced, market saturation should not be an issue, the PS3 and 360 are still doing fine.

The Wii's decline before 2011 when the Project Cafe rumours started in earnest was certainly not massive. And the PS3/360 haven't sold as much as the Wii, so of course they're not as affected by saturation. (Yet)