All right, choose ONE game for each system you are familiar. No wishy washy choices, just choose one or none if you don’t know.
Atari 2600: Adventure
**NES: Final Fantasy III(J)
**SNES: Final Fantasy VI(III in the USA)
N64: Ocarina of Time
PSOne: Chrono Cross
Gamecube: Tales of Symphonia
PS2: Okami
**
By all means, include systems I’ve not experienced enough of.
Atari 2600: Before my time. 
NES: Super Mario Bros. 3
SNES: Final Fantasy 3 (US version. Chrono Trigger is a very close second.)
Genesis: Phantasy Star 4
PS1: Metal Gear Solid (Valkyrie Profile in another close second)
Dreamcast: Skies of Arcadia
PS2: God of War 2 (This is a tough one. The PS2’s library is exceptionally large, with a lot standout titles. MGS3, FF12, Persona 3 and GTA: SA could all just as easily go in this space. I haven’t played Persona 4 yet or it might belong here to. I basically just flipped a coin.)
Gamecube: Tales of Symphonia
XBOX: Shenmue 2 (This was another tough one but for completely different reasons. I didn’t care for Halo or Ninja Gaiden and I never owned that many games for this system. I do love the Shenmue games though.)
XBOX 360: Fallout 3 (Mass Effect deserves an honorable mention here.)
PS3: Valkyria Chronicles. (I know this game was just released but I just purchased it last week and I’m having a blast with it. It deserves more attention than it’s getting and it’s everything I wished Operation Darkness had been last year for the 360. As a Metal Gear fan I wanted to say MGS 4 here but I’m honestly having more fun with VC.)
This was more difficult that I had anticipated when I started this message. Most of the high profile systems have a lot of excellent games and I enjoyed different ones for different reasons.I know this is heavily weighted toward RPG’s but I do honestly play other genres and enjoy them a great deal. Maybe it’s just because I spend so much more time on RPG’s than other games they weigh more heavily in my recollections.
If I had to choose a best PC game of all time I’d say Planescape: Torment. That game was phenomenal.
Also, the 360 and PS3 are both the “best titles” so far. I reserve the right to change my mind in the future on both of them. 
NES: Super Tecmo Bowl
SNES: The Legend of Zelda: A Link to the Past
N64: Goldeneye 007
I respect Adventure for bringing some concepts to console land that are now fundamental parts of the medium (check out my SDMB profile if you don’t believe me) but I can’t call it the greatest. I have to go with Yar’s Revenge since it did the best job of bringing a new arcade style game of exceptional quality to the 2600.
For the Intelivision there’s no option other than Utopia. Not the AD&D games, not the voice games, not even Kool-Aid Man.
The Colecovision was kind of game poor but they did have the best port of Donkey Kong.
On the Atari 5200 I think they had an excellent port of Star Wars: The Arcade Game.
(I honestly don’t remember enough about my Odyssey games to point one one as best; the only one I can remember clearly is that Pac-Man clone with the bugs and that wasn’t even for the first system. Same goes for Vectrix and I’m skipping over all the computers since the PC with it’s continuous upgrade cycle since 1981 makes it really confusing.)
On the NES I have to go with Super Mario Brothers 2; the US one. I thought it was a much tighter game than Mario 3 and you have to have a platformer for the console that defined platformers.
On the Sega Master System/Game Gear I have to go with their port of Sonic the Hedgehog. The US market for that platform got taken down hard by Nintendo but I’ve got to respect this fine adaptation of the game.
On the original Gameboy I have to select Tetris; there were better versions of Tetris out there but the Gameboy one was special and brought the game to its biggest audience. (I can’t say Pokemon since I’ve never managed to complete one of the games. I just get bored with them and eventually walk away.)
On the Lynx there’s only one game anyone remembers: Slime World.
With the PC Engine/TG-16 I have a fondness for Bomberman '93 and all of those people who will throw out arguments for Dracula X can bite me (not literally vampire fans).
For the Genesis I’ll pick Gunstar Heroes mainly because it’s like Contra on acid and I feel bad for not really having a place to slip contra in elsewhere in the list.
Super NES has many options to choose from but I have to go with the unsurpassed Zelda: A Link to the Past. The 3D versions never played half as well.
I think everyone’s favorite Jaguar game is Trevor McFur. Just kidding there, obviously Alien Vs. Predator; the game so nice they redid it right.
On the Saturn I have to go with Evangelion: Girlfriend of Steel not because it’s a good game but it just kind of represents why I have a Saturn; it was easy to plug in a cartridge so it could use Japanese games and I got a bunch of not very good but memorable to me anime tie-ins. If you want a real one I’ll go with Puzzle Fighter because that’s the game I had the most fun with my Saturn playing.
It’s another narrow field with the N64 so I’ll take the easy route and say Mario 64.
For the PSX it’s the opposite problem; it’s a huge library… of stuff that was done better elsewhere several years before. If I had to select a console for the “vast wasteland” award this would be it. Still to pick one of the gems out of the muck I’ll go with Castlevania: Symphony of the Night and hit the mute button every time a character talks.
On that theme with the Gameboy Advance I happen to like Metroid Fusion but maybe if I ever get around to Mother 3 it’ll take the top spot.
For the Dreamcast I have to select MARVEL! VERSUS! CAPCOM! TWO! They might not put that punctuation on the box but it’s definitely there when people say it. The Dreamcast was exceptional for fighting games and this is easily the best of them.
On the PS2 I have to choose that model of zen in a shiny disk Katamari Damacy. There’s a game that never fails to make me smile.
And spinning once more to the flipside on the Gamecube I have a lot of respect for Eternal Darkness since I had previously claimed that there was no way a Call of Cthulhu video game could ever be effective. It’s a shame that none of the official Cthulhu games are this good (yes, I’m including Shadow of the Comet).
Looking over the Xbox library I’ll go with X-Men Legends as a good way to bring superheroes, action, and some RPG elements together in a way that is a lot of fun with four players. Yeah it was on every platform but as a rule I found that for multiplatform games the XBox versions were usually the best.
With the Nintendo DS I’ll pick the second Phoenix Wright game (the subtitles get jumbled up on me for those, sorry) mainly because a series of interactive mysteries is what got me to buy one. They’re not without their flaws but they are well designed enough and priced right at the sweet spot that I get my value for them.
On the Wii there are a lot of interesting choices in the upper tier but I’ll single out Resident Evil 4 for being the first playable console FPS (or close enough to first person given then viewpoint). Yes, I’m including the Halo series and Goldeneye in that. For once the controls didn’t feel like playing underwater.
Finally on the XBox 360 (I don’t own one but I’ve played quite a few games on them) I’ll select Left 4 Dead mainly because we had a good time playing the co-op mode. Too bad it’s so short.
(All that and I’m sure I’m missing a few…)
NES: Super Mario Bros.
N64: 007 Goldeneye
PS1: Castlevania: Symphony of the Night
**XBox: ** Knights of the Old Republic
**X360: ** Bioshock
PS3: LittleBIGPlanet
Gamecube: Metroid Prime
Wii: Mario Galaxy
These are just my personal favorites:
Atari 2600: Dig Dug
NES: Final Fantasy
SNES: Final Fantasy 2 (with Legend of Zelda: A Link to the Past a close 2nd)
Genesis: X-Men
PS1: Final Fantasy 7 (my all-time favorite game)
PS2: Dark Cloud
PC: Baldur’s Gate
Atari 2600: Megamania
NES: Super Mario 2 (Hard pick)
SNES: Final Fantasy 3 (Extremely hard pick. Too many top contenders.)
Genesis: Sonic the Hedgehog 2
Sega CD Lunar
N64: Harvest Moon 64 (The best version of one of my favorite series.)
Saturn: Virtua Fighter Remix
PS1: Gran Turismo
Gamecube: Animal Crossing
Xbox: Knights of the Old Republic
Dreamcast: Tony Hawk 2
PS2: GTA: San Andreas (Like the SNES, it’s nearly impossible to pick just one.)
Xbox 360: Rock Band 2 (Very tough choice.)
Wii: Twilight Princess
Sega Master System: Ys: The Vanished Omens
Sega Mega Drive: Sonic 3
Sega 32X: Doom 32X
Sega Saturn: Daytona USA
Xbox 360: Lost Odyssey
BBC Micro/Acorn/Amstrad: Elite
Amiga: Shadow of the Beast
DOS: Lemmings 2: The Tribes
NES: Snake, Rattle & Roll
Gameboy: Motocross Maniacs
Game Gear: Game Gear Shinobi
Mega Drive/Genesis: Cannon Fodder
SNES: Syndicate
PlayStation: Gran Turismo
Nintendo 64: 007: Goldeneye
PS2: Grand Theft Auto: San Andreas
GameCube: Metroid: Prime
Windows 95+: Half Life 2
Jesus Christ. I’ve spent a lot of my life playing videogames!
This is a mix of what I really think was best and what my personal favorites were. For my money, the original F-Zero would have been the best game ever if it had a 2-player mode. GTA 3 was a much bigger deal than San Andreas, but the latter was more fun to play. Civilization 2 would be my personal favorite in PC gaming. I’ve had it since 1995-ish and I still dig it out to play now.
Atari 2600: River Raid
NES: Super Mario Brothers
SNES: Super Mario World
N64: Mario Kart 64
Xbox: Knights of the Old Republic / Psychonauts (tie)
Wii: Mario Galaxy
I never owned any Sega system, a Gamecube, or any Sony system.
Atari 2600: Solaris
Though I think my credibility in making recommendations for the Atari 2600 is somewhat tainted by the fact that I played and enjoyed E.T: The Extraterrestrial as a child. Honestly, I don’t know what I was thinking.
NES: Mother
A quirky role-playing game about a boy in rural America who becomes caught up in the legacy of his great-grandfather’s paranormal research and sets out on a quest with some young friends to save the Earth from an alien invader with some strange connection to his family. Strange, funny, and not “officially” available outside of Japan – it was translated by Nintendo, but never released. You have to find a ROM dump of the unreleased prototype to play it in English.
SNES: Secret of Evermore
There are a lot of contenders on the Super Nintendo, and a lot of the games others have already mentioned in this category are favorites of mine as well. I picked Secret of Evermore because it really is a lovely little game (with a beautiful soundtrack by Jeremy Soule) that IMHO doesn’t get nearly enough recognition.
N64: Ocarina of Time
Gamecube: Super Smash Bros.: Melee
Lovable Nintendo mascots beating the everloving crap out of each other. What’s not to love?
Wii: Twilight Princess
PlayStation: Final Fantasy Tactics
Chrono Cross and Final Fantasy IX being close runners-up.
Gameboy Advance: Mother 3
Mother 3 is also probably my choice for “best video game ever, period.” Third installment of the Mother series, sequel to the SNES classic EarthBound, Mother 3 was sadly never released outside of Japan – fortunately, there’s an excellent fan translation available if you want to play it in English. Words really can’t do this game justice; it has a story that’s heartwarming and heartrending at the same time, and it is one of the very few games that has ever made me cry. I can’t recommend it enough.
Dragon 32; The King. Bascially a rip off of Donkey Kong, a pretty blatant one too.
Spectrum 48k+; Tank Simulator 3D. Another rip off, whatever you call that old game with wireframe graphics and tank’s doing battle.
NES; Super Mario Bros. 3. A nice little platformer, enough special stuff to make it more enjoyable than the first. The 2nd in the series was just a little too offbeat for my liking.
Gameboy; Tetris. Nothing else is so damned playable. Again and again and again…
PC; Civilisation. In any guise really, we’ve all wanted to rule and conquer like this, now we can do so, from the comfort of our own bedroom!
SNES; Super Mario World. Just so perfectly paced and designed for anyone to play. (Close second Zelda: A Link to the Past)
N64; Goldeneye; Without the multiplayer, it would still be a blast, but slaying your friends just makes it no. 1.
Gamecube; Zelda Windwaker; Beats the multiplayer aspect of Mario Kart, a really beautiful game to look at and play.
Originally, Battletank, and later Battlezone. What’s a Dragon 32?
A computer from Wales of all places (Wiki article). We got it from my Mum’s brother but a short while later picked up our Spectrum 48k+, so we didn’t really use it for too long. It seemed a lot easier to use than the Speccie, the keyboard didn’t have the plethora of symbols and multifunctions on each key for a start.
Huh… neat. We had a BBC Micro 32, which used the same processor that now runs your mobile phone, weirdly enough.
Atari 2600 - Combat! or Demon Attack. Combat is just pure Multiplayer awesome, and who can ever forget the damned little demons kamikaze attack?
NES - SM3, Contra
SNES - Super Mario World. No contest. One of the best platformers ever… I still pick this game up occasionally and play it, which is very rare. Add the absolutely superb art design which makes it still a great looking game by todays standards… The sinble biggest issue I can think of is the flying mode of the cape made a lot of levels very trivial. More powerup storage woulda been nice too, so you didn’t have to go back to the donut secret all the time.
PS1 - Wipeout XL, or Castlevania: Symphony of the Night. The Wipeout series had awesome tracks(racing and musical), and I have never yet seen such a difficult, unforgiving racing game. Castlevania, proving that the 2d platformer is far from dead even in an age of 3d.
PS2 - Shadow of the Colossus. Ok, not the best gameplay ever, but it is certainly one of the most unique games I have ever played, and is absolutely gorgeous.
Xbox - Halo. With a qualifier… Granted that it uses a lot of elements from other games and stories, it still puts it all together nearly flawlessly(except the Library) and has outstanding direction and acting. By itself its only above average though… Played Co-op… easily one of the best times I’ve ever had playing a game.
I go a step further and say it’s the best video game of all time. Maybe I was just the perfect age when it came out, but that was the pinnacle for me. I don’t know if it can ever be topped.
I agree (even about the library-- that level sucked), and I would add that it has bar none the best music in a video game ever.
nes . mike tyson’s punch-out!
atari lynx . todd’s adventures in slime world
sega genesis . sonic the hedgehog 2
snes . final fantasy II
sega cd . sonic cd
n64 . zelda: ocarina of time
playstation . final fantasy VII
xbox . halo
360 . rock band 2
wii . zelda: twilight princess
i think zelda: ocarina of time is the best videogame ever.
i think sonic cd is easily the best sonic videogame.
No way… that would have to be Killer Instinct. Or Streets of Rage, if we’re correcting for system capabilities.
Check out how popular it is on OCRemix.org if you don’t believe me.
How do you get the fan translation? You can PM me if you want. I’m very curious about this.