1. If you mean you like the French language:
* Me gusta el francés. (This is the most common and straightforward way to say it.)
2. If you mean you like French culture, food, etc.:
* Me gusta la cultura francesa. (I like French culture)
* Me gusta la comida francesa. (I like French food)
* Me gusta todo lo francés. (I like everything French)
3. If you mean you like French people:
* Me gustan los franceses. (I like French people)
Remember that the choice of how to say it depends on the context.