Robert DeNiro Michael Cain Samuel L. Jackson Eric Roberts 
Answer: Eric Roberts
There is a game, for the unfamiliar, called “The Six Degrees of Kevin Bacon” wherein participants pick an actor or actress and try to, in as few hops as possible, link them to another actor or actress. For example, the actor Alec Baldwin has a “Bacon Number” of “1” because he starred in the film She’s Having a Baby with Kevin Bacon in 1988. Conversely, Star Trek creator Gene Roddenberry has a Bacon Number of “3” because to get from Gene to Kevin you have to go from Star Trek Adventure (1991) where Roddenberry appeared with Nichelle Nichols, to Star Trek III: The Search for Spock (1984) where Nichelle Nichols appeared with Frank Welker, to Balto (1995) where Frank Welker starred with Kevin Bacon, thus three hops.
Now, with the general framework of the game in mind, here’s a shocker: despite the fame Bacon has achieved as the center of the Hollywood universe courtesy of the popularity of this game, he isn’t actually the most connected actor in Hollywood. A group of students at the University of Virginia put together The Oracle of Bacon project to scrape all the data on the Internet Movie Database in order to create a speedy Six Degrees of Kevin Bacon fact checker and, in the process, discovered that Kevin Bacon himself was actually fairly poorly connected according to the rules of the game named in his honor. Far from number one, his degree of connection to everyone else fluctuates, but he’s typically around the 411th most connected person in Hollywood.
If you crunch the numbers and look for the actor or actress who has the least degrees of separation from the highest number of other actors or actresses, you find the most connected person in all of Hollywood is Eric Roberts, brother of Julia Roberts. Not only has Eric Roberts starred in a huge number of films, but he has also starred in a huge number of films that feature other prolific actors and actresses which gives him the lowest degree of separation rating. If you’re looking to connect Eric to another actor, you’re never more than “2.83” degrees away.
Image courtesy of Eva Rinaldi.