Formal:
* Splendid: Emphasizes brilliance and grandeur.
* Grand: Suggests impressive size and scale.
* Sublime: Implies awe-inspiring beauty and grandeur.
* Exquisite: Highlights delicate beauty and perfection.
* Exemplary: Implies a model of excellence.
* Spectacular: Emphasizes visual impact and impressiveness.
* Extraordinary: Highlights something remarkable and exceptional.
Informal:
* Awesome: Common and emphasizes impressive size or power.
* Superb: Means excellent and highly enjoyable.
* Fabulous: Expresses admiration and enthusiasm.
* Wonderful: Indicates great pleasure and enjoyment.
* Brilliant: Suggests intelligence and intellectual brilliance.
* Amazing: Emphasizes wonder and surprise.
The best synonym depends on the context and the specific meaning you want to express.