The game opens with a beautifully rendered battle between an orc and human as a raven watches. You can see the grimaces of effort and hear grunts of pain as the warriors fight, until what appears to be a falling meteor strikes the ground beside them. It unfolds itself to be a giant humanoid rock creature, a demon called an infernal as we later find out, and the orc and human gaze together in horror upon this new enemy, their battle temporarily forgotten.
If it sounds epic, that's because it is. Blizzard has always been famous for their dramatic cinematics, and for sheer breathtaking power and inspiration to play the game, the only competitor is Diablo 2. The light-weight graphics engine guarantees that even at their most intense, the Warcraft 3 cinematics play smoothly without loss of sound or skipping, even on low-end computers.
As the cinematics develop between each part of the single-player campaign, a poignant tale of love, death, betrayal, and corruption highlights the dramatic range of the game. Considering this is the same game where various Easter Eggs have character voices spouting comedy and one of the most famous quotes is "zug-zug", this depth to the main story is refreshing.
The only drawback is their sheer length. Blizzard has always walked a fine line between serious and casual games, and one of the places they take some extra time is in the cinematics. As 3-d engines become more realistic, cinematic cut-scenes become more involved, and in the case of Blizzard games this isn't always a good thing. All three of the major franchises are very visceral and high action; long cinematics only break our rhythm and tempt us to escape out of them. Considering all the work the writers and graphic designers put out creating these scenes, having most players ignore them because they detract from the flow of gameplay is a waste.