Travolta has actually turned down several big movie roles throughout his career that ended up going to either Tom Hanks or Richard Gere (Splash and American Gigolo are just two examples). When he was offered the role of Forrest, he turned it down in order to star as Vincent Vega in Pulp Fiction.
In 2007, MTV asked him: “Do you have any regrets? Like, ‘Oh, if I had done Forrest Gump or Chicago, what might have been?'” to which Travolta replied, “No, because if I didn’t do something Tom Hanks did, then I did something else that was equally interesting or fun. Or, if I didn’t do something Richard Gere did, I did something equally well. But I feel good about some I gave up because other careers were created.”