a fan
A fan is just someone who likes something, whether it’s a person, a food, or a sport. They probably think it’s the best thing ever.
My friend is a fan of pizza. He eats it every day and says it's the best food ever.
My mom is a fan of my dad. She says he's perfect, even though he's not.
My little brother is a fan of video games. He plays them all day and says they're the best.