Ocarina of time

NES:  To the best of my limited knowledge, Super Mario Brothers 3
SNES: Star Fox.  Terrific music and incredibly satisfying gameplay.
N64:  I'll give this spot to Tetrisphere.
Gamecube:  Definitely Melee
PS2:      

            Okami

PC - Civ 1-4, Daggerfall, Red Alert
SNES - Super Mario Kart
GC - Eternal Darkness
PS3 - MGS4,
Wii - MK Wii,
DS - MK DS

NES - IF I had to choose one (I thought about this over the past few hours) I would have to go with Super Mario Bros. It was just so much more than what was in the public's eye at the time. I mean, it WAS mistaken for the original launch title. I'm trying to recall if there were any linear side-scrolling games prior to it. I know it was the first I and most people played. I mean this was about as significant as the jump to (true) 3D. Tetris, SMB3, TMNTII, Contra are all worthy titles (in that order) but the impact SMB had was massive. Note* Double Dragon was generally not as well recieved in the home as in the arcade which is why I wouldn't consider it and Legend of Zelda only because Adventure and Pitfall! were big on the Atari. LoZ was still epic but not as genre bending as the others. It did influence RPGish quality though. oh and Dragon Warrior > Final Fantasy!!!!

Game Gear = Road Rash (It was the only port that served to be more polished than the Genesis version, to my recollection)

Game Boy = Super Mario Land; Few titles on GB (original only) stood out as really being similar to that at home exp. For me my gameboy was like a junkie fix. It was something to tide me over till I got home. Blades of steel was really nice but it wasn't NES, and it made me squint a lot. Paperboy, Tetris, Double Dribble and many other titles were kinda like NES * 0.5. Super Mario Land held similar portion 4-3 instead of 8-4 levels, but it had it's own kind of originality to it that made it special. I don't think I played another GB game as much as this. FF series was crap (I still bought one though) and the Zelda game was close to SML but the rest trailed. M2:RoS (Metroid 2) would have been better but to me the game was so bland visually and I got lost constantly because of it. Total lack of shading.

the only true masterpiece I've ever played is Planescape Torment on the pc. PLAY IT NOW!

GB: Tetris

GBA: Advance Wars

SNES: Super Mario World, Secret of Evermore, Super Metroid

N64: The Legend of Zelda: Ocarina of Time, Perfect Dark, Super Mario 64, GoldenEye 007

Wii: Super Mario Galaxy, Super Smash Bros. Brawl, Mario Kart Wii

PC: Baldur's Gate I & II, Heroes of Might and Magic III, Command & Conquer, Half-Life, StarCraft

Master System- Wonder Boy
NES- SMB
SNES- Zelda ALTTP
Mega Drive- Sonic the Headghog
Mega CD- Snatcher
Saturn- Nights
PS1- Fade to Black
N64- Zelda OoT
Dreamcast- Shenmue1+2
PS2- SotC+GoW2
GC- Metroid Prime
XBox- Chronicles of Riddick
PS3- Uncharted
360- GeoW

A n N64 piece of magic would be Banjo- Kazooie, funny, challenging, and huge all in one.

There has been two true masterpieces of gaming

Xenogears and Starcraft.

PC - Final Fantasy 7 (yea, I played the PC-version), Starcraft, Warcraft 3

PS2 - ICO, Shadow of the Colossus (although I've played both of them on the PS3)

Saturn - Panzer Dragoon Saga