SNES.....just cuz the NES was the catalyst for what the gaming market is today doesn't necessarily make it better than the SNES in my eyes.
The SNES has many of the greatest RPG's (if not games) of ALL time - Mario RPG, Earthbound, FF3, Chrono Trigger, Zelda A Link to the Past (> Legend of Zelda IMO), Breath of Fire series, Lufia series - to name a few. Some other great games are Mario Cart, Super Smash TV, NBA Jam, Kirby Super Star, Harvest Moon, Killer Instinct, Super Punch Out, Donkey Kong, Contra 3, Turtle in Time, F-Zero, Yoshi's Island, Star Fox, Super Metroid....the list goes on.
I understand some of these series originally started on NES (Punch Out, Metroid etc) but I believe if I was stuck on an island and I had to choose between NES with the entire library and SNES with the entire library, I'd go with the SNES every single time. Both systems are great, but I have significantly more childhood memories from the SNES than I did from the NES from playing 2 player (Mario Kart, NBA Jam, Contra etc) with my brother to the first time I killed Kefka, the Mana Beast, Gigas or Lavos. Maybe I'm biased because of the great RPG's....