FIFA 10 is a good football title but it's not without its problems. Compare it with Pro Evo 10 before making a decision.
Ok enough with the PES comparisons. FIFA 10 is a very good football title. The graphics are identical to those seen in FIFA 09 which is a good thing since FIFA 09 was definitely a looker. Team AI has been improved, goal keepers are more realistic, headers feel better, and more plausible match outcomes are seen in simmed matches in Manager mode. Online play is excellent as usual and this is really one area that Konami have a long ways to go to catch up on.
In terms of negatives, team AI still needs a lot of work; players run into each other on too regular a basis (it even happens to the computer on the World Class difficulty), and goal keepers are still unrealistic making super human saves yet fluffing absolutely simple shots. Players often don't tend to stick to their respective playing zones and matches often get messy with players running willy nilly with no discernible strategy (once again this also happens to the computer on World Class). Players still seem a bit too homogeneous, with star players like Messi and Torres not standing out enough from their talented but less stellar peers. There is also, to me at least, the fact that FIFA still doesn't feel "right". It's really hard to explain but I just don't feel FIFA captures football as well as Pro Evo does (I know, I know, I haven't kept my promise about the comparisons).
I love football and I love football games so I'll end up getting both FIFA 10 (for online play) and Pro Evo 10 (for offline play). Both games are worthy purchases for a football fan; which one you chose is really pretty much up to you. You're bound to enjoy one of them.