The graphics, sound effects, and control are all top notch and are an improvement over FIFA 11 overall, so there is no reason to spend much time talking about them.
What is significant are the new changes to FIFA 12, and how they have affected the gameplay. The most noticeable two are the 1) Tactical defending and 2) Player impact engine.
I will explain both briefly to give newcomers an idea of what to expect.
1) Tactical Defending: Arguably the biggest and most significant change is the new defending system. No longer can you hold down A and B and watch as your defense swarms the hapless attacker automatically
In FIFA 12, you have to position properly and time your tackles well (as in reality) in order to gain possession of the ball. Mis-timed or poor tackles will often result in the attacker blowing past you or a foul and/or booking.
I MUST WARN YOU, that this can be VERY FRUSTRATING at times when you are learning the new system as it is not very forgiving. For those of you intimidated by this there is an option to revert to the old system called "Legacy" (Identical to FIFA 11's system). But I HIGHLY recommend you take the time and effort to master the new defensive system, because it is highly realistic, extremely rewarding when you do that perfect tackle, and required if you want to master online play.
2) Player impact engine: No more ghost players going through each other, players collide with each other when in the same physical space (shocking I know!). This can also result in injuries, some which are horrific and others which are just plain hilarious as your players fly around like ragdolls.
The system isn't perfect and I've heard of a few bugs about it, but I haven't encountered any yet so I can't confirm. It is a welcome change though and, for the most part, adds to the realism of the game.
This is by far the best soccer/football game out there, and even if you're not a big fan of the sport, chances are that you will enjoy this immensely fun and well designed game. Just about everything has been improved, and the extras (such as support your club) are just icing on the cake.
Now if you'll excuse me, writing this review has already taken enough of my precious FIFA 12 playtime!