You could give Real Madrid a go. Ronaldo is pretty over-powered, so throw him up front and score heaps of goals.
Ok so that wasn't the most serious answer. The beauty of football is that it can be played a variety of ways, and any team can be successful on their day. Other things can influence this as well, such as the formation you play, or the custom tactics that you use. At the end of the day, you need a team that compliments the style of football you like to play.
Possession / Passing Game
This style focusses on keeping the ball, and is my favourite style of the game. Basically in defence you want to get the ball back as quick as you can, and then keep it. Be patient and build up your attacks slowly, moving the ball from one side of the pitch to the other with short, sharp passes.
The main aspect to attacking with this style is the use of off the ball runs. If you're running into space with the ball, tap R1 (on Playstation) a couple of times and send a few guys on runs to create some space. When you give a pass with a midfielder or attacker, in many cases you'll want to hold R1 again to ensure you are creating passing options for the next man.
Team: You can't go past the classic footballing teams. Barcelona or Arsenal. Great passers, they're fast, and they can finish.
Formation: You'll probably want to use a 4-3-3 variation. This gives you both depth and width, and natural triangles for passing opportunities.
Tactics: High movement, Free Form attacks, High Pressure defence all over the pitch.
My most hated style of the game. Not because it's ineffective, but because I find it ugly. It can definately be effective, for example you'll create lots of 2v3 and 3v4 opportunities, where a mistake from a defender can create a chance on goal. Don't forget to attack down the wings either, as having a couple of finishers in the box can net you a few goals.
Team: What you're looking for is a team with 2 strong attackers, who can hold the ball up and protect it, then finish. Think along the lines of Manchester United, with Rooney and Berbatov up front. Or Manchester City, with Tevez and Adebayor up front.
Formation: Some variation of 4-4-2 should do the trick. Flat midfield if you play down the flanks, or a diamond to give more depth in the midfield.
Tactics: I can't think of any specific tactics that would help, however you want the 2 front men sitting as high as possible.
This style can be very effective given the right team, a really fast team. For most of the match you'll be just waiting. Let the other team have the ball, and play defensively. Don't put too much pressure on them, or you'll tire out you're players. Then wait for an opportune moment, for example when you're defending a corner, and from there you rush out of defence with 2 or 3 passes, and have a 3v3 or better attacking chance.
Team: Someone fast. Arsenal come to mind, or perhaps Real Madrid.
Formation: Play defensively. I'd suggest a 4-2-3-1 for this style of play. You get both depth and width, to break fast from defence, and go either wide or down the middle.
Tactics: Bring down the amount of defensive pressure you're team puts on in defence, and make the attacking moves Free Form with risky, medium to long passes.
Hope it helps.