1. Half-Life
2. Metal Gear Solid
3. Diablo 2

Only Three? Why, there are plenty of gems out there I love, I'll go by the title nonetheless.
Three games that I spent the most time on and deserve a heart emoticon. A text one, I have standards...
1. Wizball (C64)
The music! Catellite! The Colours! Pure Awesomeness!
2. The original C&C (DOS)
From that opening FMV, you know this is going to be good.
3. Deus Ex (Windows)
What can one say other than what has already been said?

Hmm. Tough one, this.
1) Thief
2) System Shock 2
3) Mechwarrior 2
But my god there are so many more I could have picked....! Half-Life, Deus Ex, Dark Forces / Jedi Knight, Unreal Tournament, Doom, Duke Nukem....

1. Final Fantasy VII & VIII
2.Total Annihilation
3. SWAT 4 - Great multiplayer!

Outcast,
Anachronox,
Little big adventure.

Way too hard so in no particular order:
Zone of The Enders 2: The 2nd Runner
Diablo II
Planescape Torment

1. Thief
2. Fallout
3. Starcraft

1. Heroes of Might and Magic II
2. Deus Ex
3. Fallout
(according to what I told PC Gamer, these are followed by Giants: Citizen Kabuto, Chronicles of Riddick, Team Fortress 2, Starcraft, Startopia, The Secret of Monkey Island and Psychonauts)

I really can't say I'm sure about this, but I think at at this moment the three games that do spring to mind are:
Monkey Island 2
Civilization IV
Grim Fandango

Fallout 2
C&C 95
Civ IV

1. Fallout
2. Monkey Island
3. Deus Ex
4. Grim Fandango
5. Psychonauts

1.Soccer Kid. (amiga , snes, pc )
2. Jagged Alliance 2 ( pc )
3. Fallout 2 ( pc )

1. Half-Life 2
2. Mafia
3. Psychonauts

Too many favorites to list...but if I go by what games I'm most likely to continue playing for a while:
ESP Ra.De.
Dodging shit, blowing up shit, and grabbing gold in its purest, most refined form yet. Runner-up is Titanion, without the gold but still plenty of opportunities to turn enemy fire into points with a single kill.
Virtua Fighter 5
Less joystick-twisting and combo memorizing, more thinking. Runner-up is The Last Blade 1, with a little more joystick-twisting but a similar addictive quality.
Hostile Waters: Antaeus Rising
Squad action/strategy has never been done quite like this, nor better than it. Runner-up is Battlezone PC remake, with slightly harder squad management but still the same action kick that RTS sorely needs now.

It's really difficult to think this generally, so I'll let help me. It has a rather poor PC-only database though, so [url=http://www.databaze-her.cz/uzivatele/triple-t/hodnocene-hry/]these are more of representative than absolutely right:
Cave Story
Metal Gear Solid
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