Garwoofoo
Nicked this thread idea from another forum because I thought it was quite interesting.
Wikipedia has a list of the "best video games of all time", aggregated from various review scores. Of the 178, which haven't you played? (I'd have spoilered it for space, but carriage returns don't work in spoiler tags on this forum coughanikicough)
Full list:
Pong
Zork
Space Invaders
Asteroids
Pac-Man
Defender
Donkey Kong
Frogger
Galaga
Joust
Ms. Pac-Man
Pitfall
Robotron 2084
Elite
Tetris
Gauntlet
Super Mario Bros.
The Legend of Zelda
Contra
Double Dragon
Mike Tyson's Punch-Out
R-Type
Mega Man 2
Ninja Gaiden (NES)
Super Mario Bros. 3
Prince of Persia (1989)
Simcity (1989)
The Secret of Monkey Island
Super Mario World
The Legend of Zelda: A Link to the Past
Lemmings
Monkey Island 2: LeChuck's Revenge
Sonic the Hedgehog
Street Fighter 2
Sonic the Hedgehog 2
Super Mario Kart
Wolfenstein 3D
Day of the Tentacle
Daytona USA
Doom (1993)
The Legend of Zelda: Link's Awakening
Mortal Kombat 2
Myst
NBA Jam
Phantasy Star 4
Sam & Max Hit the Road
Secret of Mana
Simcity 2000
Donkey Kong Country
Earthbound
Final Fantasy 6
Star Wars: TIE Fighter
Super Metroid
X-COM: UFO Defense
Chrono Trigger
Warcraft 2: Tides of Darkness
Wipeout
Yoshi's Island
Civilization 2
Command & Conquer: Red Alert
Nights into Dreams
Pokemon Red & Blue
Quake
Resident Evil (1996)
Super Mario 64
Tomb Raider (1996)
Castlevania: Symphony of the Night
Final Fantasy Tactics
Final Fantasy 7
Goldeneye
Gran Turismo
Quake 2
Star Fox 64
Star Wars: Jedi Knight: Dark Forces 2
Tekken 3
Ultima Online
Dance Dance Revolution
Grim Fandango
Half-Life
The Legend of Zelda: Ocarina of Time
Metal Gear Solid
Panzer Dragoon Saga
Resident Evil 2 (1998)
Soul Calibur
Starcraft
Thief: The Dark Project
Age of Empires 2
Everquest
Homeworld
Planescape Torment
Shenmue
Silent Hill
System Shock 2
Baldur's Gate 2: Shadows of Amn
Counter-Strike
Deus Ex
Diablo 2
Jet Grind Radio
The Legend of Zelda: Majora's Mask
The Sims
Tony Hawk's Pro Skater 2
Advance Wars
Animal Crossing
Final Fantasy X
Gran Turismo 3: A-Spec
Grand Theft Auto 3
Halo
Ico
Max Payne
Metal Gear Solid 2: Sons of Liberty
Rez
Silent Hill 2
Super Smash Bros. Melee
Grand Theft Auto: Vice City
The Legend of Zelda: The Wind Waker
Metroid Prime
Prince of Persia: The Sands of Time
Star Wars: Knights of the Old Republic
Warioware Inc: Mega Microgames
Burnout 3: Takedown
Grand Theft Auto: San Andreas
Half-Life 2
Katamari Damacy
Metal Gear Solid 3: Snake Eater
World of Warcraft
Civilization 4
Devil May Cry 3: Dante's Awakening
God of War (2005)
Guitar Hero
Resident Evil 4
Shadow of the Colossus
Splinter Cell: Chaos Theory
The Elder Scrolls 4: Oblivion
Gears of War
Okami
Wii Sports
Bioshock
Call of Duty 4: Modern Warfare
God of War 2
Halo 3
Portal
Super Mario Galaxy
Team Fortress 2
Braid
Dead Space
Fallout 3
Grand Theft Auto 4
Left 4 Dead
Littlebigplanet
Persona 4
Spelunky
Assassin's Creed 2
Batman: Arkham Asylum
Uncharted 2: Among Thieves
Limbo
Mass Effect 2
Red Dead Redemption
Rock Band 3
Super Mario Galaxy 2
Super Meat Boy
Batman: Arkham City
Dark Souls
The Elder Scrolls 5: Skyrim
Minecraft
Portal 2
Dishonored
Fire Emblem: Awakening
Journey
Mass Effect 3
Telltale's The Walking Dead Season 1
Dota 2
Grand Theft Auto 5
The Last of Us
Bloodborne
The Witcher 3: Wild Hunt
Inside
Overwatch
The Legend of Zelda: Breath of the Wild
I'm missing a surprisingly high number - 26 (where I've never played any of the game whatsoever):
Spoiler - click to showContra, Mike Tyson's Punch-Out, Ninja Gaiden (NES), Daytona USA, NBA Jam, Phantasy Star 4, Secret of Mana, Earthbound, X-COM: UFO Defense, Nights into Dreams, Ultima Online, Panzer Dragoon Saga, Starcraft, Everquest, Homeworld, Max Payne, Devil May Cry 3: Dante's Awakening, Splinter Cell: Chaos Theory, Call of Duty 4: Modern Warfare, Dead Space, Red Dead Redemption, Dark Souls, Mass Effect 3, Dota 2, The Witcher 3: Wild Hunt, Overwatch
Dishonored just snuck on there as I started it a few days ago, and The Witcher 3 has been on my list to play for ages, but the others have totally passed me by.
I'm guessing keeping up with lists of this type will become even harder over time due to the sheer amount of stuff being released these days.