AMOROSO, for me it's hard to say. Some of our youth players like Vranjes and Leko are looking really good. But you can't count them because as you said they're very young.
Simic is a canditate, he's still young, but old enough to be considered for this.
Boban is a great talent, but injured alot, and this season will be his last. It's hard to pick him as the best player because of his injury problems. His season ended early because of his latest injury.
Stanic seems like he can't be injured. The guy really is a beast. He isn't nearly as technically skilled as a Boban or Prosinecki, but he's a very good player who contributes a lot to the team, and is always playing hard.
Because of Boban's injuries and Prosinecki's lack of fitness, I'd give the nod to Stanic
On their best days, I'd definately say Prosinecki, followed closely by Boban. Suker has been a great striker, but IMHO, midfielders are far more important to the team.