Mine is Metal Gear Solid 3 Subsistence; soon to be MGS4 Guns of the Patriots.MGS brings such uniqueness to to gaming as well as excellent gameplay and a connecting story and developed characters, all of which continue to evolve with time

I have a tie between The Legend of Zelda: The Ocarina of Time and Jak and Daxter the Precursor Legacy.
Zelda self-explainatory
Jak&Daxter was my first game I had for PS2, it was amazing I was addicted. It made me a big fan of the series and buy other great platformers like the Ratchet and Clank series.

Kingdom Hearts 1 & 2 , I haven't played anything better

The Legend of Zelda: Ocarina of Time is the greatest game ever made. No experience can ever compare to playing it for the first time. With a large, beautiful world, great levels, and excellent controls, this game defines greatness. No other game I have played even comes close to this one. This game is perfection. This game alone is a good enough reason to own a Nintendo 64.

Gameboy Camera( anyone remember) I loved that game. when I was 7 I took pictures of everything, edit them, made movies, I never seemed to stop playing it.

Pokemon Silver, when I was younger that was all I knew, pokemon this and pokemon that. I hope they do a remake for the DS.

It would either have to be Final Fantasy VI or Tetris.

Final Fantasy VI-- While the gameplay is bad the music, story, and characters are all incredible and they tell so much with so little.

Tetris-- Yeah, this game just rocks. I can sit there for hours and play this game without even realizing it.

Okami.....because....because....

Just because.

Kinda a three way tie.

1. The Sims 2 (PC) - Ok, I know, but it's got so much replay value and extremely addicting. I have to put it on here. I've always liked simulation games and this is pretty much the peak.

2. Super Mario Galaxy (Wii) - Pure creativity, some of the best music I've ever heard, very addicting and extremely fun, plus excellent controls. This is really the only truly "amazing" 3D platformer I've ever played. I played some great 3D platformers, but all of them have bad flaws. SMG has pretty much none and defines the genre. Truly one of the best games ever made and definitely the best for this generation.

3. The Legend of Zelda: The Wind Waker (GCN) - This game is a masterpiece. It has some of the best controls I've seen in a game, the best graphics I've seen in the game, some of the best music I've ever heard, tons of sidequests, and a truly epic adventure, with an excellent story and ending. Pretty much the only reason to own a GCN.

If I HAD to rank them I guess

1. Super Mario Galaxy

2. The Sims 2 

3. The Legend of Zelda: The Wind Waker

Oblivion. It has everything. By far the best game ever.

Other notable all time great are:
Age of Empires II
Warlords II
Return to Castle Wolfenstein/Enemy Territory
Kameo
Dark Forces II: Jedi Knight
Dark Age of Camelot
Conquests of Camelot
Boulder Dash
Gabriel Knight: The beast from within

There are so many... but Oblivion rules.