My favourites are in this order Brazil, Spain, Argentina
Sadly Germany will probably not play a big role in this tournament. They have problems at too many positions.
Goalkeeper: Neuer has a shoulder injury and may not be able to recover in time. Weidenfeller though is a pretty good backup.
Centre Back: Hummels, Boateng, Mertesacker - no problems here
Right-Back: Lahm probaly will play in midfield so Großkreutz will play - solid player but nothing spectacular
Left-Back: Probably Schmelzer - probably the weakest link in the German team. He just lacks quality.
Defensive Midfield: Schweinsteiger and Khedira both had knee injuries and probably won't be any near their normal form. Lahm is also lightly injured. Lars Bender won't be able to play at the world cup. That leaves Kroos as the only fit player at that position. Huge problems.
Offensive Midfield: Lots of quality options and tremendous depth: Özil, Reus, Müller, Götze, Schürrle, Podolski
Forward: an aging Klose (36years old) and a tottally inexperienced Volland. I guess they will just play without a real striker.