Starcraft 1 and Warcraft 3 were something powerful, that we haven't really seen since: A platform for distributed game design and testing. You could play mods

Starcraft 1 and Warcraft 3 were something powerful, that we haven't really seen since: A platform for distributed game design and testing. You could play mods as easily as the game itself. Designers could fork each other's maps. This spawned incredible numbers of games. In addition to the MOBA (League of Legends, DotA) genre, Starcraft 1 mods also popularized the Tower Defense genre (Plants vs. Zombies, Desktop Tower Defense). It was frustrating to see Blizzard's designers drop the ball with Starcraft 2. The original discovery model -- Host a game with a mod, or see hosted games -- was simple and imperfect, but effective. Blizzard failed to understand why the original system worked, and "fixed" what wasn't broken.