Are you someone/something's biggest fan?
PrevNode LinkI hate the “my fandom/fanhood is bigger than yours” meme. Thus, I can be a fan, a big fan, or a very big fan of something, but will not claim superiority or superlativity.
Also note that I try to be a non-fanatic, sincere, and critical, fan. If I am unhappy with a work of a creator, of whom I am a fan, I may inform them that I feel this way about it.