"I don't think Will does get upstaged because his reaction is always funnier than what is actually happening. That is also the reason Tommy is funnier than Will"

This quote by Barry Sonnenfeld is referring to the comedic dynamic between Will Smith and Tommy Lee Jones in the Men in Black films. Sonnenfeld is saying that Will Smith does not get upstaged by Tommy Lee Jones since his responses to the occasions in the movies are frequently funnier than the occasions themselves. This is why Tommy Lee Jones is funnier than Will Smith, because his responses to the occasions are typically funnier than the events themselves. Sonnenfeld is implying that Will Smith's comical timing and reactions are what make him so funny, which Tommy Lee Jones has the ability to capitalize on this by playing off of Will Smith's responses. This comedic vibrant in between the two actors is what makes the Men in Black movies so successful.