The sentence translates directly to "this is your favorite movie?", because with spanish, a question can just be phrased as a statement with a question mark/verbal accent slapped on.
We use this in english, it just tends to be more incredulous or surprised, as in "you like this movie?"
Película is feminine, so it would be favorita. The gender of the speaker has no bearing on the adjective here. because that adjective is tied to the subject, película.
It applies to self in cases like tú eres mi favorito hermano or Estoy muy cansada when the speaker is female.