The more traditional way to praise the food is to say 'Hoppe ga ochiru'. Curiously, it means that 'the food is so nice that your cheeks are falling off' which is a symbolic way to express the delicacy of the food.
The traditional margherita pizza ingredients are mozzarella cheese, tomato sauce, and basil. Because the toppings are so simple, they must be top quality.
If something tastes better than you expected, you could use the word wow to express your surprise. If you say something tastes amazing, you're saying it tastes even better than great or really good.