A subscription service included with online play at no extra charge, that allows full access to the NES-N64 library. Pick the game you're thinking of, play it. Simple.
GCN and Wii games should be available via download, preferably with some level of remastering.
I'd also like to see some graphic remasters of classic 8-16 bit games with beautiful new pixel graphics, and/or sequels using modern visuals and sound. Kid Icarus with an Ori paint job? Hells yes.
And lastly having access to more modern games that never appeared on Nintendo consoles would be great. Steam-like access to old titles like FF8 and so on.
Nintendo should be striving for industry leading excellence with their online services and their back-catelogue should be an area of major strength. That's how it was in the early Wii days.
