First of all, FIFA 2004 provides for the first time in FIFA games history a career mode, which lasts for 5 years.
However, it lacks a more important thing, which is fast and realistic gameplay.
The game is also lacking realism, as this version of the game is assasignated with more trick keys which are not helpful at all. It lacks the simple and real football, as the tricks or manuevrs you do seem to be from other planet.
There is also a new feature in the game, called Off-the ball control, which enables you to take yor other players without the ball, while you control it, and move them where you want. This will be a helpful feature both for new and old fans of the series.
Argueably, the defence organized by AI is difficult to get through, but after a few matches you will realize that the defense is making the same moves again and again, and you will find a way to score easier.
The AI becomes very hard to beat when the score difference is big, no matter the difficulty level you play in. This happens because the CPU tries to have the score being as closer as possible.
Another disadvantage of the game is the interfaces. The structure of the menus in FIFA 2004 are very confusing.
FIFA 2004 is a game with many pros, but with other cons at the same time. You should try the demo first before buying the game.