Formal:
* C'est fabuleux/fabuleuse. (This is the most literal translation and is appropriate for formal settings.)
* C'est magnifique. (This translates to "it is magnificent" and is a more elegant option.)
* C'est extraordinaire. (This means "it is extraordinary" and is a more dramatic choice.)
Informal:
* C'est génial! (This means "it's awesome" and is a very common expression.)
* C'est super! (This means "it's great" and is also very common.)
* C'est top! (This means "it's top" and is a slang term.)
Other options:
* C'est incroyable. (This means "it's incredible" and is a more emphatic way to say it's fabulous.)
* C'est époustouflant. (This means "it's breathtaking" and is a very poetic way to say it's fabulous.)
The best way to choose the right phrase is to consider the context and your audience.