The free games that a service like that would give, people would have already bought them and Nintendo should get more return than the 50usd yearly which is around 10 VC NES games.
A service like that would make Nintendo owners buy even less eShop titles, heck I only buy eShop titles when they go on discount. If they started offering a subscription I wouldn't buy anything digital and just play what the Nintendo overlords decide to throw my way.







