This is not polite. It is better to say: You are a very interesting person.

"I like your face" is an odd sounding sentence. I think you are trying to say "I think you are pretty"(if it's a girl) or "I think you are handsome." (for a guy). And yes, if someone said one of these things it would be an appropriate response to feel happy, because it's a compliment.

It's not impolite, but it's a weird sentence, usually you like more than the face, you can say "You're pretty" and that would be more common and polite. Saying "I like your face" it's like saying you are only liking the face, but nothing else though. People usually prefers to be known by their personality and not by their looks :P