Video Games
For video games nobody beats the Final Fantasy series... nobody. It's game after game of brilliance - perfectly matched to the game.
...and if you're listing games that just group songs that have been released prior, look up the definition of OST.
Television
The new Battlestar Galactica is waaaay up there. Game of thrones deserves a mention for the credits. Dexter creates mood really well from the soundtrack. I'd go with Battlestar.
Film
This is a huge... huge list. Braveheart obviously deserves a mention. The LOTR trilogy had phenomenal music. Last of the Mohicans is kindof a one-tricky pony, but it's a great trick. Batman Begins, The Matrix, Glory, Legends of the Fall, Road to Perdition, Shawshank Redemption, American Beauty, Edward Scissorhands, Medicine Man, Star Wars, Crash, Gladiator, Perfect Storm, Saving Private Ryan, Dances with Wolves, Truman Show, Dark City, Chariots of Fire, 1492 Conquest of Paradise, Dragon the Bruce Lee Story, Crimson Tide, DaVinci Code, Bram Stoker's Dracula, Apollo 13, the 5th Element...
Very hard to pick....
My first reaction is that it's between Braveheart and Gladiator. Each was perfect for the respective movie, but I'd have to give the nod to Braveheart.