Basically "favorite" is a noun to mean a thing/person one prefers above others. It can be used as kind of an adjective but it is an imperfect adjective with some restrictions in usage. For example, you cannot say "This is favorite to me" to mean "This is my favorite". "She is my favorite actress" is semantically like "She is (my favorite)'s actress". So you cannot put periphrastic words such as "more" and "most" between "my" and "favorite".
and thats my cut and paste for the year