I just thought I might try to help out those who can't decide between getting this title or letting it pass by.
I am personally very impressed with FIFA 09 for the Wii. I was looking for a new football game, since playing PES 08 Wii for some time started to bore me and the club/player content was outdated. So I bought FIFA 09 without any high hopes, but the game sure did surpass my expectations. The gameplay is kinda similar to PES 08 where you point to pass and in some cases dribble. The shooting system is also like FIFA 08 and you have the "strenght meter" on the shots that you didnt have in PES 08. The graphics are far better than PES 08 and FIFA 08, but still nowhere near PS3/360 level. The defending is also far better in my opinion. It feels like you really have control of the defence, rather than panicing (as in PES 08) while seeing your opposite team strikers come against you with the ball.
Few other thing that I thought EA did a good job with are the different modes that the Wii version have, specially the online modes which are really fun (interactive league for example). It's not just 1v1 matches such as PES 08, but you can also have ranked/unranked matches which gives the online mode more depth.
The only thing that the game suffers from are the graphics (if you compare it to PS3/360, but thats expected) and a few gameplay elements that PES 08 introduced (such as dragging arrows to decide the running points for free players). I still prefer FIFA 09 to be ther better game and think that the game as a whole far surpasses PES 08. Since PES 09 comes out in summer 09? I would say get this game if you're a football fan.
Sorry if something isn't clear, it's really late here and I am about to sleep. If there's anything you're wondering, feel free to ask me.