The best four teams at present are Brazil, Spain, Germany and Argentina, who are the strong favourites to make the semi-finals.
The next thing you need to focus on is the conditions. There's a strong correlation between which continent the finals takes place in, and the winners. I think the conditions will not suit Germany's game, as they'll sap the intensive energy that their game requires. As good as Spain have been over the last decade or so, some of their key players are ageing, and they lack an absolute world quality striker that is a finisher (although the same could be said of Germany).
Because Argentina have an abundance of these (Messi, Aguero, Higuain, and probably others too -- note, it seems unlikely that Tevez will make their squad), alongside having defensive solidity, I'm going to plump for them in the final against the host nation. Brazil are good, and well managed, but it's only really Neymar who's world class, and this World Cup might just come a few years too early for him. Mind you, Messi hasn't performed really in previous World Cups, and this might just be the perfect moment for him to establish him in the all-time greats pantheon.