I think in terms of the experience, and uniqueness, I'd have to go with Wii. I had so much fun playing unique games like Wii Sports with friends and family and Wii fit for the first time.
But in terms of sheer strength of the game library, I have to go with the Super NES. Just an incredible lineup of great games. Super Mario World, Yoshi's Island, Donkey Kong Country 1 and 2, Final Fight, Turtles in Time, Super Castlevania, Super Mario RPG, Final Fantasy III, Secret of Mana, Uniracers, Virtual Bart (well I liked it at least), Zelda: A Link to the Past, F-Zero, Chrono Trigger, Earthworm Jim, Sunset Riders, Zombies Ate My Neighbors, Secret of Evermore, NBA Jam, Super Metroid, Super R-Type, Kirby Super Star, Tetris and Dr. Mario, Super Mario Allstars, Pilotwings, Super Mario Kart, Starfox, Earthbound... The list just goes on and on and on.