Ya know, I was one of the rare Americans who owned a Master System and NOT a NES! I had an Amiga, and so I decided to skip the NES. When the Master System came out I got that because I thought it would be like having an NES with slightly better graphics.
Well, the SMS has slightly better graphics, but it's not as good as owning an NES.
I can only say that now many years later, because thanks to emulation I've been able to try nearly every game made for both systems. And in terms of sheer numbers of quality games, the NES has an endless supply. Everything from classic arcade conversions, to action, platformers, adventure, RPG, shooters... Just tons and tons of really good games with some decent 8bit graphics and sound.
So while I do respect the good games the SMS has, it just can't compare in terms of numbers. And so many NES games were exclusives, stuff like Kirby, Megaman, Castlevanias, Zelda, Final Fantasy etc. - SMS owners missed out on many great games.
And that's why people are excited by NES on GP32.
Cuz it means a HUGE library of great games added to the list of stuff us lucky GP32 owners can play. It's mind-blowing - you can probably fit 500 NES games on an SMC! =P Or more?!