What does it mean to have a favourite?
Is it a preference: Given the choice, you’d rather have your favourite.
Is it a scale issue: Your favourite is something you always want more of.
Is it a judgement: Your favourite is the one you think is the best.
Is it a relationships: Your favourite is the one that make you happiest (or some other positive emotion).
Is it circumstantial: It’s the best you’ve found (so far).