I don't think you can make a wrong decision. All three restaurants you mentioned are worthwhile for different reasons. Personally, I love Kouzzina and don't understand all the criticism. It's actually one of my favorites non-signature restaurants on property. I suppose the menu can seem a bit exotic or unusual for people unaccustomed to Greek or Mediterranean cuisine, but if you like that type of food, I strongly recommend Kouzzina.
Are you using a dining plan? That definitely will influence the advice you'll receive. I presume you aren't, because Shula's does not participate in the plan. It is also, I should add, extremely expensive, even by Disney standards. I almost hesitate to suggest it based on that factor alone, especially if you have acceptable steakhouses in your hometown.