I'd say Alonso vs Hamilton. Alonso was really sore about being beaten by Hamilton. It didn't help that they were team mates. So. he'd want to prove that he's better by beating Hamilton in a different car. And win the championship at the same time.
But what I'm really looking forward to is Piquet Jr vs Alonso. Will the former prove too fast for Alonso? Will we see a repeat of what happened last year?