I really can't single out any single game so I'll just drop my top 5:

Metroid Prime 3, The best FP shooting controls on any console to date, great adventure, list just goes on and on and on.

Warcraft 2, my first true PC game. It ensured that the PC claimed me and never let me go, because of this game I will always value the PC more than any console.

Super Mario Bros 3, I don't even know where to begin, probably the game that has sucked the most out of my life, and that's including the 150+ days of /played on WoW.

SSBM, The shallow fighting game which turned out to be extremely deep, I still have my original SSBM disk from 6 or so years ago.

Quake 2, the first true Deathmatch game which I played. Incredibly fun and FPSes are still one of my top genres right up there with RTS and RPG.

I still play it a few times just for old times sake, But when it first came out I was so addicted to it!!! If that makes any sense?

anymore of you dudes

FFX.. why? I dunno. It just is, heh.

Favorite game LoZ:OoT first game I ever beat and nothing compares to that, actatually beat it five times in total and nothing can compare.

Paper Mario

I freaking love that game before, now, and forever

I remember drawing maps from town to town and writing down the price for certain items to see which item like the thunder was the cheapest at, I also beat the extras like the dojo and gotten 999 coins ( the highest you coud get) and also the highest level you could possibly get. The music in this game is the best, each music fits with each world just right! the designs of the desert and the fortresses/ dungeons are epic!

this gen mgs4/cod4/gta4=very addictive
all time=goldeneye, sanandreas

The Legend Of Zelda: Majora's Mask

It took the gameplay a Ocarina and added a much darker and in depth story.

Favorite game this generation
Metal Gear Solid 4: Guns of the Patriots
The story is amazing, the gameplay is my favorite and definitely beats any other previous MG/MGS game or any previous sneaking game, the online is addictive and is always different every game you have.

Favorite game of ALL time
Final Fantasy X
Being the first game i ever truly played for a very very long period of time (200+ hours in total) and the first FF i played (although not my favorite that goes to FFVI). I found the story very very good and i could play it over and over again and not get bored, the gameplay was as any FF before it was and it was the last one with random encounters (which is a downside for the series but also a plus side).

Wow - too many games to chose from. The following four all struck me as something special and would probably come as close to 'favourite' for me as any game could:

Elite
Grim Fandango
Deus Ex
Ico