Which country spends the most on board & card games?
So looking online I found this from 2015.

It says 


  More are sold per capita in Germany than anywhere else on earth


Magic the Gathering is big, with something like 20 million players worldwide, however that will pale in comparison to board game sales so I'd be likely to ignore card games as they won't add a huge amount overall compared to board games.

So in conclusion, Germany looks like the best bet