One other thing to consider is not only cost to license games, but to have them registered with the appropriate certifiers (ESRB, etc.). Apparently this is very costly and Nintendo loses money on those games that don't get downloaded just on this aspect alone. If you look at the top downloads month after month, they are the Mario games. There is very little movement amongst the other titles in popularity - good or bad, a lot of retro games are just too obscure to make a profit.