MGS, MSG2 and FFX had a huge impact on me. Still, I think something is missing and I lack the ultimate single-player experience and probably even anything that would be close enough. I want something deeper, something more varied.

Deus Ex

The game has everything:

• Deeply involved story of conspiracy, terrorism, technology and world government.
• a variety of amazing weapons and items,
• futuristic sci-fi cyber-punk conspiracy based future setting,
• lots of playstyles (complete stealth, assault, tank, stealth take downs, lethal vs non-lethal attacks etc.) ,
• amazing player choice in everything,
• deeply interactive (you can read papers/books, hack ATMs, smoke, use toilets, play basketball, eat, drink and get drunk and get high among many others ), 
• Player choices actually have major effects on the story deciding who lives or dies and moral choices are different shades of grey
• Amazing abilities: fast speed/jumping, stealth, vision enhancements, strength, invisibility, spy drones, health regeneration to mention a few
• Body parts had different health bars; if your legs were shot to bits you could only crawl; if your limbs were damaged you couldn't aim properly, torso or head = death
• A wide array of skills and upgrading each one had tangible benefits; again, player choice and playstyles
• True hybrid FPS/RPG gameplay
• Basically, the deepest and most involving single-player video game experience ever created
• It predicted 9/11

I played it through about 6 times (possibly more, I lost count) and always have to have it installed on my computer. I pretty much did everything in the game. However, even on my 5th playthrough, the wealth of options and player choice was so great, I was still finding new stuff and areas I hadn't previously discovered. I cannot praise this game enough.

Chrono Trigger

No contest.

Mass Effect, the first one.

Forget StarWars, StarTrek or everything else... this is the best Sci-Fi universe and you get to play inside it!

True RPG (too bad ME2 is not)

Awesome music

Strong atmosphere
[PLUS]
Squad team shooter
[PLUS]
Deep story and universe
[PLUS]
Top of the edge graphic (for 2007)
[PLUS]
Excellent dialogue mechanic
[PLUS]
Bioware

=

Best Game of All Time

Final Fantasy 6, Ocarina of Time and Dragon Force.

The Legend Of Zelda: Majora's Mask and SW: Knights of the Old Republic

Majora's Mask. But Super Mario Galaxy came a close second.

1 Tales of Symphonia: great characters story and amazing combat system.

2 Uncharted 2: Same as above

3 Havy Rain: A little short but overall very innovative gameplay and over all you you feel like and adredaline junkie driving backwards through the highway or an asshole because you wouldn't cut your finger off to save your son.

I can't pick between Metal Gear Solid Peace Walker and Donkey Kong Country 2...I will not pick they are both my favorite all time!

System Shock 2