Tough to say.. Wii had the most quantity of 3rd party games, but Gamecube probably had the best ones. It was actually one of my favorite Nintendo consoles for third party games outside SNES. And it's probably the only Nintendo console where I actually prefer more 3rd (and 2nd) party games than Nintendo ones..
Tales of Symphonia, Eternal Darkness, Phantasy Star Online, Sonic Adventure 2 Battle, Super Monkey Ball, Resident Evil series, Timesplitters 2, Soul Calibur 2, Tony Hawk 3, etc.. Some of these aren't just still my favorite Gamecube games but favorite GAMES period.
N64 wasn't good for 3rd party but certainly great when talking 2nd party, as Rare back in the 90s were probably my favorite gaming company second only to Nintendo.
Wii U? Bleh..
"We hold these truths to be self-evident - all men and women created by the, go-you know.. you know the thing!" - Joe Biden
