Also, on the 3DS if you are into Pokémon, there's the VC GBC games (Red/Blue/Yellow; Gold, Silver, Crystal). Not only it's the only place they can be legally purchased, but they are compatible with Pokémon Bank, making them the only way to transfer 8bit Pokémon to modern games.
That was my pick. I took the opportunity to complete my VC Pokemon collection whilst I still could. Also I got the Pokemon TCG which is also on VC.
Something else to note is the VC version of Crystal allows you to get the GS Ball and Celebi, which was never available in the original release outside of Japan. This is something I wish they did more of in the remakes (like the unused locations for the mythical Pokemon in Diamond & Pearl).