Hopefully the Wii. Some Wii games of course would need pointer movement translated to joystick movement, and many would also need motion controls translated to standard controls so that people aren't force to play with motion.
I don't really see any other systems coming. I assume Nintendo has to pay for any non-Nintendo game added to it, which is why most of the games on there were made by Nintendo. Genesis is the one non-Nintendo retro system that was actually popular, so of any of the options that one made the most sense, and that's the one NSO has. Non-Nintendo games are rare on NSO because that cuts into the profit from NSO, and if they add more entire non-Nintendo systems beyond the Genesis that would cut a lot more into NSO's profit. I don't see that happening, unless the fees they'd have to pay for this stuff is super low. This isn't like the virtual console where every game had it's own price, every single non-Nintendo game (from Nintendo systems or not) on NSO cuts out NSO profits, and thus also makes it more likely they'll have to make a third higher tier, and quite frankly the other systems were never very popular so just aren't worth that for Nintendo nor NSO users. Makes a lot more sense for companies to just put out a compilation on Switch and Switch 2 (as has already been done a bunch on Switch) than this stuff get crammed onto NSO.
If Nintendo can finish up their NES, GB, SNES, Genesis, N64 collections on NSO over the next couple years, and build out the GC collection this gen as well as a Wii collection, that'd be a superb retro games service on NSO and I'd consider that complete. Anything more would not be worth it from either business-side (less profit), consumer-side (higher cost), or both.







