I don't think you're understanding the point of the article. Yes, emulators have been around for quite a long time, but none of them are perfect, which is the purpose of this guy's undertaking to create this emulator requiring a 3GHz CPU.
The Wii isn't going to be around forever: those will start to fail in a number of years. In addition, not every single NES game is available on the Wii virtual console, anyway.
The emulators on the wii virtual console are not accurate at all, not in the way that byuu is talking about. Also the games get heavily patched for that purpose, as well as the emulator being patched per-game.
I think I may have only bought the Donkey Kong Country series of games for the Wii VC. It worked well enough, but I imagine that there were indeed issues with the emulation on the Wii. I didn't do any research on it so I couldn't comment on that either.
The one thing I realized after the last few years is that you can't count on game companies to do backwards compatibility forever. Microsoft (understandably) gave up on patching the 360 over and over again to expand the original Xbox library of playable games on the 360, and Sony stopped selling the PS3 models that had the PS2 hardware directly on-board(not to mention "Other OS" support, but I digress).
Back compat is only useful in a business sense in that consumers don't have to decide between new console and no games or old console and lots of games. Once the new console has lots of games, that simply becomes the only option.
The Wii isn't going to be around forever: those will start to fail in a number of years. In addition, not every single NES game is available on the Wii virtual console, anyway.