I think in life to know what you really like, you also need to know what you don't like. Some of my friends are real film buffs and they watch lots of films, including some bad or mediocre ones as well as "must-see" films. I've gotten to the stage where I usually avoid films I know will be bad (apart from notorious "so bad it's good" films like Flash Gordon, I loved that one), because I don't care to see them, but my friends say watching awful films like The Adventures of Pluto Nash and Gigli helps them to remember why the best films are so good.