John Travolta suggested Sylvester Stallone to producer Robert Stigwood after Travolta saw Rocky III (1982) while on vacation in Hawaii. Travolta loved the film, and told Stigwood that if he could pull off sequels that well, he would be the ideal choice for directing Staying Alive.
Yep. Sylvester gets no respect because he is Italian.
He wrote Rocky and has directed MANY of the movies he has starred in that were huge hits. The whole concept of The Expendables was his idea and he has directed all the films.