In "Magnificent Seven," which I just watched again, the commentary of Walter Mirisch, the producer, said that ALL the brass thought Horst Bucholz would steal the movie, when in fact it was James Coburn (aside from the obvious stars, Brenner and McQueen) who only had seven lines, who stole the movie.
Caine is a great actor because he WORKS, and not every piece of work is a masterpiece. Bogart did crap, too.