As they say in the financial services industry, past performance is no guarantee of future returns.   Those best seller lists dont show that during the GameCube and N64 generations that nintendo was badly beaten. And its happening again.

Only if they would at least break even from the sales.

Other than giving existing WiiU owners a few extra games to play, what would this achieve? It's unlikely to attract many new users to the system, because they can get these same games elsewhere.

So in effect Nintendo would be paying money to sell someone else's games to existing users of their system who might otherwise be buying Nintendo games......

There's a question I could ask here but I'll let you figure out what it is.

Nintendo's success or failure will always be tied to whether the unique experiences it bring to the market has a broad enough appeal. When they do that the third parties get on board. Nintendo's problem last gen was weak hardware appeal for 3rd parties, and a weak audience for the type of games 3rd parties usually make. Their problem this gen is weak software appeal for the wider market and to a lesser extent weak hardware.

Buying ports will do nothing to help because the best versions will always be on PS4 and very occasionally Xb one, and the second best version will be on Xb one.

I can see an argument along the lines of if the multiplats are there, then lack of multiplats won't be a barrier to buying. Trouble is Nintendo still needs the exclusive content that will make people want to buy. And it doesn't have that.