Argentina? No thanks. Not calling up Cambiasso (best defensive midfielder around nowadays), Lucho, Lisandro Lopez (Palermo who? He's old now, and not good enough for the national team) and Aimar is definitely a way to get fucked over.
England? Not too big on them, they're a very psychologically fragile team (look at how many times they've lost penalty shootouts and you'll see). Still, lots of their players are on a great run of form (see: Lampard) and they might make an impact.
Italy? Again, no thanks. Not calling up one of the best scorers in the Serie A (Miccoli) along with one of the best overall Italian players (Cassano), no matter how undisciplined he is, is not the way to go. The nucleus of this team is an 8th place Serie A Juventus squad. Not a huge fan of them either, because of their rather cheap antics.
Spain? Perfect on every level. Main, main contenders for winning this, and I'd say they have a 50% chance. They've the best of the world in almost every position (arguable, but hey).
France? They shouldn't be there in the first place, but I'd say they have o.k. chances. Not calling up Benzema and Nasri is to shame, though. Never liked Raymond Domenech.
Brazil? Not calling up Ronaldinho and Pato may prove costly to this side... Nonetheless they've a lot of GREAT players at some positions, while weakened on some places. Definitely 2nd contenders.
Germany? One of the weakest Germany squads in recent times... They're very disciplined and mentally strong, though, so they might have a shot.
I'd go with a list like this on my opinion on the probability of certain national teams winning the WC2010:
1. Spain
2. Brazil
3. Holland (you heard me)
4. Portugal
5. England
Note: Is it just me or every national team manager has decided to piss off the world by not calling up the national team stars in some cases? (Benzema, Ronaldinho, etc)