Comment subjective list below, by genre and platform (Score 1) 382
These are in no particular order of preference, as I heavily prefer these to most other games. I'll try to put them in broad categories and mention the platform.
- Megalomania - arcade style falling threat shooter - Atari 2600
- Gauntlet - cooperative overhead maze runner - arcade (some home systems may suffice, but the arcade is the best)
- Pitfall - side-scrolling platformer/runner - several, but 2600 is mine
- Axis and Allies - WWII board game - board game, Avalon Hill then some other companies. There are decent computer implementations. The Hasbro PC version is good except the AI is weak.
- chess - board game
- Spades, Euchre, Oh Heck - trick-taking card games - get Hoyle and a deck of cards, really
- Poker, especially Hold 'Em and Omaha - betting card games - get Hoyle and a deck of cards, really
- Fallout, Fallout 2 - isometric overhead CRPG - DOS (1 only), Windows, Mac OS, OS X (1 only), OnLive (I've played only on DOS/Win)
- Fallout 3, Fallout New Vegas - first person (with camera changes to 3rd over-shoulder if you like) CRPG - Windows, PS3, Xbox 360
- Half-Life, Team Fortress Classic - first-person shooters - Windows, Linux, OS X, PS2 (Half-Life only)
- Half-Life 2 - first-person shooter - Windows, Xbox, Xbox 360, PlayStation 3, OS X, Linux, NVIDIA Shield
- Unreal Tournament or Unreal Tournament 2004 (take your pick) - first-person shooter - Dreamcast, Linux,
Mac OS, Mac OS X, PlayStation 2, Windows - Trivial Pursuit - trivia board game - board game or one of many computer implementations
- Asteroids - 2d space shooter with wrap-around threats from all direction - arcade, 2600, others
- Super Mario Brothers - platform run and jump - NES
- Bionic Commando - platform run, jump, swing, and shoot - NES
- Genghis Khan - tile-based, turn-based strategy and tactics - NES, very playable on Wii virtual console version
- Final Fantasy - multi-character sing;e-player RPG-like adventure - NES
- Savage Worlds - pen and paper RPG - I've been playing RPGs for more than two decades, and this is my current personal favorite ruleset
- Scorched Earth or some version of Worms - 2d power and angle turn-based artillery with weapons upgrades - various
- Scorch3d - 3d reimagining of Scorched Earth - probably various, but I've played it on Linux
- Starcraft - RTS - Windows
- Total Annihilation - RTS - Windows
- Spring - RTS - Linux, Windows (at least)
- Supreme Commander - RTS - Windows
- Supreme Commander: Forged Alliance - RTS - Windows
- Nuclear Dawn - FPS with minor RTT/RTS aspects - Windows, Linux
- Awesomenauts - 2d platform shooter - Linux, Windows, OS X
- Risk - board game - board game with many computer interpretations
- Boggle/Super Boggle - tabletop letter dice grid word-hunt game - special
- Scrabble - crossword board game - board game, but lots of computer implementations
- Castles 2 - castle building, defense, and siege game - DOS/Windows
- Stronghold series - castle building and defense game - Windows
- Apples to Apples - party card game
- Cards Against Humanity - like Apples to Apples gone horribly inappropriate - lots of implementations since it's Creative Commons
- Colonization or FreeCol - Civiliation-style expansion game in the settling of the new world - DOS (Col), multi (FreeCol)
- Civilization series - complex simulation of competing civilizations - Windows (but check out FreeCiv
- Alpha Centauri - Sid Meier's Civ series
- Master of Orion series - simple interface, complex 4X games in space - DOS, Windows
- Mortal Kombat series - 2d fighter - lots
- Killer Instinct - 2d fighter - SNES (others? IDK)
- Street Fighter series - 2d fighter - lots
- Eternal Champions - 2d fighter - Genesis
- Mechwarrior 4 - first-person mech combat - Windows
- Armored Core - first-person mech combat - PS/2