20 Games That Changed Gaming Forever

The editors at PC World have counted down the twenty video games that they feel "changed gaming forever". As is usually the case in these types of lists, they completely ignore any games released prior to 1995. Why mention popular MUDs, Ultima Online, or EverQuest, when you can just jump ahead several years and drop World of Warcraft into the #3 position?
Blizzard Entertainment created an entire planet inside of a video game, and the result was a revolution. This online game was so game-changing that it instantly legitimized the entire genre of massively multiplayer online (MMO) games and, ultimately, earned a subscriber roster that outnumbers some European countries.

Why It Was Innovative:

How many games have been so addictive and engaging that entire subcultures are created around it? World of Warcraft was by no means the first MMO, but it was the game that perfected the rules and the experience, with a richly detailed, persistent universe for players to explore, and constant expansions ensuring that their characters would continue to grow and change as the game aged. Since the game's best treasures and biggest quests often required dozens of players to band together, WoW encouraged people to communicate both inside and outside the world of Azeroth, making the human element the secret heart of World of Warcraft.