Formal:
* Une expérience formidable: This is a very common and formal way to say "a great experience."
* Une expérience extraordinaire: This emphasizes the exceptional nature of the experience.
* Une expérience inoubliable: This means "an unforgettable experience," highlighting its lasting impact.
Informal:
* Une super expérience: This is a casual and common way to say "a great experience."
* Une expérience géniale: This means "an awesome experience," emphasizing its coolness or fun factor.
* Un super moment: This literally means "a super moment" and can be used to describe a positive experience, even if it's not a full-fledged experience.
Other possibilities:
* Une expérience enrichissante: This means "a rewarding experience," highlighting its positive impact on you.
* Une expérience positive: This is a simple and neutral way to say "a great experience."
* Une expérience agréable: This means "a pleasant experience," focusing on the positive sensations it brought.
The best phrase to use will depend on the specific situation and your desired level of formality.