Formal:
* J'ai beaucoup apprécié le film. (I greatly appreciated the film.) - This is the most formal option.
* J'ai trouvé le film très agréable. (I found the film very enjoyable.) - This is a slightly less formal option.
Informal:
* J'ai aimé le film. (I liked the film.) - This is the most common and informal way to say it.
* Le film m'a plu. (The film pleased me.) - This is another informal option.
* J'ai bien aimé le film. (I liked the film a lot.) - This is a slightly more enthusiastic version of "J'ai aimé le film".
More specific:
* J'ai adoré le film. (I loved the film.) - This conveys a stronger liking.
* Le film était vraiment génial. (The film was really great.) - This emphasizes how much you liked it.
You can choose the best option based on the context and your relationship with the person you are speaking to.