DotA 2

Dota 2 takes its name from the Warcraft III mod Defense of the Ancients, a drastic change to that stock real-time strategy title, which pits two teams of five players against each other in highly competitive, 40-minute or longer matches. Unlike most RTSes, DotA has each player controlling a single hero who levels up and stockpiles gold to purchase powerful equipment and consumables. As computer-controlled armies continually spawn and rush the enemy's base, players are responsible for using their powerful heroes to turn the tide of the battle in their favor.

DotA enjoys such unprecedented popularity for a number of interconnected reasons. The game has a skill curve as long and as wide as Counter-Strike or StarCraft; expert players dominate matches with lesser-skilled individuals solely through manual dexterity and hard-won knowledge. Extensive upgrade paths allow players to combine items into more powerful versions, gaining thousands of hit points or powerful life-stealing attacks. Team play is hugely rewarded; though the map is large enough for all ten players to spread out and fight creeps on their own without anyone engaging anyone else directly, late-game play is almost invariably centered around giant 3v3 or even 5v5 team fights.

Valve founder and boss Gabe Newell thinks that ongoing service and value creation over a game's lifespan is the new reality of game development. "IceFrog was one of the smartest people we've ever met about doing that, and he was doing it with both hands tied behind his back, so to speak," Newell says. The company plans on approaching Dota 2 with the same dedication that won it the fanatical devotion of the Team Fortress 2 community, pushing out dozens of updates that do everything from adding new hats to fixing balance issues to introducing entire new match types for free.