My list is hardly set in stone, they line up changes from time to time:
My top 20 games of all time:
God of War 2 (PS2)
Panzer Dragoon Saga (SAT)
Virtua Fighter 4: Evolution (PS2)
Half-Life 2 (PC)
Ikaruga (DC)
Deus Ex (PC)
Starcraft (PC)
Earthbound (SNES)
Fallout 2 (PC)
Metal Gear Solid 4 (PS3)
Okami (PS2)
Castlevania: Symphony of the Night (PS1)
Knights of the Old Republic (PC)
Metal Gear Solid 3: Subsistence (PS2)
Metroid Prime (GC)
Fallout (PC)
Crush (PSP)
Contra: Hard Corps (GEN)
Megaman X (SNES)
Civilization II (PC)
Current gen top 5:
Metal Gear Solid 4 (PS3)
Crush (PSP)
Half-Life 2: Episode 2 (PC)
Patapon (PSP)
Spore (PC)