Great Performance in a Mediocre Movie
 

List them here folks.

My pick would be Monster. Charlize Theron and Christina Ricci were incredible in the film. However, the overall production was ok. If it wasn't for the two of them, it would probably be a sucky movie.

Samuel L. Jackson and Jeff Goldblum in the Great White Hype

Wasn't a very good movie, but Jackson as Fred Sultan and Goldblum as Mitchell Kane were great performances...