General:
* Amazing
* Awesome
* Brilliant
* Excellent
* Fantastic
* Great
* Magnificent
* Marvelous
* Splendid
* Terrific
Positive and enthusiastic:
* Delightful
* Exhilarating
* Extraordinary
* Fabulous
* Glorious
* Heavenly
* Incredible
* Phenomenal
* Sublime
Expressing admiration:
* Admirable
* Breathtaking
* Charming
* Delightful
* Elegant
* Impressive
* Striking
* Stunning
Expressing joy and pleasure:
* Blissful
* Joyful
* Pleasant
* Satisfying
* Thrilling
Expressing rarity and uniqueness:
* Exceptional
* Outstanding
* Remarkable
* Unique
Formal and literary:
* Exemplary
* Illustrious
* Magnificent
* Resplendent
* Sublime
The best synonym for "wonderful" will depend on the specific context and the emotion you want to convey.