WC: All it takes is one film to completely change how you feel about an actor.
In the cases or Nic Cage, Keanu Reeves or Adam Sandler, who show flashes of brilliance sporadically, the way audiences feel about those actors tends to be comically impermanent. And that has a lot to do with their inevitable return to dross.
Likewise, when a great actor slums it, it tarnishes their public image terribly, and adds a distasteful caveat to their former achievements. Nobody remembers Halle Berry as an Oscar winner, they remember her as the Oscar winner who then made Catwoman. That kind of thing tends to stick.