Blizzard's World of Warcraft is considered the grandfather of the modern MMORPG, and rightfully so. Many of the core mechanics which defined online multiplayer experiences were spawned from World of Warcraft. At the time of its release, the sheer scale of the world and level of immersion wowed audiences, and that has not changed. No matter the expansion, World of Warcraft's realms are some of the most expansive and diverse ever developed. Offering dozens of biomes, major locales and fortifications, the world's sheer size can easily rival that of most modern day continents.
The actual core story behind the game evolved with time, and each additional patch built upon previous events. One introduced the distant land of Pandaria during a break between the Alliance-Horde conflict. Another saw the downfall of the Lich King of the north, while the following event reshaped the entire world in ruin. The experience of following one to the next offered players a sense of weight to events few games could match. This isn't to say that World of Warcraft couldn't have fun at its own expense. Many secondary quests focused upon everything from demolishing an enemy lava cannon to making the ultimate curry for a panda on a beach.
The questing system of World of Warcraft is undeniably traditional. However, they nevertheless benefit from the experience of developers who turned it into a fine art. Every class has enough power and potential to fulfil their own quests, from healers to tanks. However, they are so notably specialised that group efforts are required to take down many key bosses. Thus forcing players to work as a team in raids and special missions. It allows players freedom to pursue their own stories, but grants benefits in operating as a group. Even after thirteen years, World of Warcraft remains a titan among MMORPG games.