1. What kind of movies do you like?
2. What kind of movie do you like?
3. What kinds of movies do you like?
Are all the sentences grammatical?
Especially, what about #2? Is #2 the same as #1?
All grammatically correct. No, #1 is not the same as #2. In #1 you ask about movies, plural and #2 you merely ask about one movie. Essentially you could get the same answer.
All three sentences are grammatically correct. However, there is a subtle difference in meaning between sentence #2 and the other two sentences.
Sentence #1 and #3 both use the plural form "movies," indicating that there are multiple types or categories of movies that you like. It suggests that you have a varied taste in movies and enjoy watching a range of genres.
Sentence #2 uses the singular form "movie," suggesting that there is a specific type or category of movie that you enjoy. It implies that you have a preference for a particular genre or style of film.
So, while all three sentences are grammatically correct, sentence #2 implies a more specific preference compared to the other two sentences.