Formal:
* C'est brillant. (This is the most common and literal translation.)
* C'est génial. (This means "it's great" or "it's amazing" and is more informal.)
* C'est remarquable. (This emphasizes the exceptional quality or originality of something.)
Informal:
* C'est top ! (This is a very casual way to say "it's great" or "it's awesome".)
* C'est super ! (This is similar to "top" but slightly more formal.)
* C'est incroyable ! (This emphasizes the surprising or unbelievable nature of something.)
Other options:
* C'est extraordinaire. (This is a more formal and literary way to say "it's extraordinary.")
* C'est éblouissant. (This means "it's dazzling" and implies a visual brilliance.)
* C'est fantastique. (This means "it's fantastic" and is a more enthusiastic way to say "it's great.")
The best way to choose the right phrase depends on the specific situation and your relationship with the person you're speaking to.