How to talk about your favorite person or thing in Greek.
Remember: Think beforehand if what you are going to talk about is masculine, feminine or neutral so that you choose the correct form from the three options corresponding to the three genders.
So for example: if you want to talk about your favorite actor the phrase would be «Ο αγαπημένΟΣ μου ηθοποιός είναι Ο + name of the actor» (in capital letters the article, the ending of the adjective corresponding at the gender of the noun)

if you want to talk about your favorite greek singer then you would say: «Η αγαπημενΗ μου τραγουδίστρια είναι Η + the name of the singer». (Again in capital letters the article and the ending of the adjective corresponding to the gender of the noun).
And finally if you want to talk about your favorite book or film in Greek then you would say: «ΤΟ αγαπημένΟ μου βιβλίο / φιλμ είναι ΤΟ + the title of the book or film.

However, pay attention: if you want to talk about your favorite Greek island (which in Greek is neutral “το νησί”) the phrase would be:

«ΤΟ αγαπημένΟ μου νησί είναι Η Τήνος». Because most of the Greek islands in -ος are female.