Like all Blizzard games, WarCraft III has an extremely robust multiplayer component. Blizzard's Battle.net makes online play simple and swift with a host of play options, including hero-centered scenarios. And if you're really serious about multiplayer, you can enter tournaments and slug it out with other players via the player-ranking ladder system. If there's one downside to multiplayer, it's that the people who play online are really good, so you'll need to bring your A-game if you want to even stand a chance.
Regardless of whether or not you're a hardcore fan of strategy games, WarCraft III's compelling story and excellent balance makes it a must-own.