FIFA 09 is arguably the king of soccer games, and the pinnacle of the series' renaissance. That means that there are big expectations for FIFA 10, the latest version of the EA classic.
While it's visually not far removed from its predecessor, the FIFA 10 PC demo will demonstrate some "under the hood" changes that really improve the game. The biggest is the introduction of 360 degree control. Your players no longer move in just eight directions, but whatever way you want. This makes control a much more subtle, and gives you greater flexibility and the ability for much more creative play.
FIFA 10's player animation has been totally revamped - they move with real character now and dribbling looks great. Your teammates have also had an intelligence upgrade, making them act more naturally, and thus less likely to do what you want them to.
FIFA 10 management has also been upgraded, perhaps in response to the richer experience in the Konami's Pro Evolution Soccer. FIFA 10 players now come with 'ambition', which affects their decisions - if your team is full of defenders, it might be difficult to convince another to join, as not playing much is rarely what a player wants to further his career.
A cleaner and more subtle game than its predecessor, FIFA 10 is quite an improvement, and another step towards a totally realistic football experience.