According to Janet Hubert-the original actress who played Aunt Viv on "The Fresh Prince of Bel Air (yes, the dark skinned one) Will Smith was the reason she got fired from the show. In her soon to be released memoir 'Perfection Is Not A Sitcom Mom', Janet writes
"Smith had people around him who made sure no one outshone him. I was happy to see Don Cheadle become the quality actor that he is, and often wondered how he made it past one episode, as Hilary's boyfriend, being such a fierce actor. No one could be on 'The Tonight Show,' that first season, except Will. And I mean no one."Damn Willie, it was like that? Hating on Aunt Viv?

I don't know, this seems a lil' hard to believe. Although, she played the role really well her character could not compete with Will's. I wouldn't even put their characters in the same category for any type of comparison.
Bitch got a book to sell DO YOU MAMA!