imo, FIFA11 was the worst in the current FIFA series....awful.
FIFA12 is a little better.
The most important improvement is the sliders, so you can alter the cpu's (and your own) passing accuracy, acceleration, etc. This makes playing against the cpu bearable in comparison with previous FIFAs, where the cpu was perfect all the time, never misplaced a pass, etc. It's still not particularly good but at least has a few hours of life in it.
The defending is also a little better now.
Career mode is also apparently much improved but I've not been able to stick at it long enough to notice because repeated play against the cpu soon gets very dull and repetitive. There's no real variety in teams and players, every team plays with the same tactics, every match feels the same and it becomes a chore to play. I'm at the stage now where I turn it on, play against the cpu for about 2 minutes and turn it off again in dismay. It's insipid and boring.
If PES introduced sliders so you could stop the cpu teams being perfect when they go into god mode, then I think there would be more longevity in it.
2 very disappointing games, frankly.