For those ages 18 and under who probably never owned a NES, you very well may not have played the NES VC games the first time around and the vNES can give a good idea what these games are like. Those of us in a demographic where the VC games are actual nostalgia, by playing the vNES we might just get that feeling out of our system. But for those who still want the game even after the vNES test, they can go ahead and buy it on the Wii's VC. The vNES also works as a great way to remember titles we wish would make their way to the VC in perfect emulation.
We do not support piracy and using the vNES as a demo solution is hardly ideal, but vNES is a nice trip down memory lane and a good way to see what VC titles you'd like to see in the future.