13. Jack Nicholson - Michael Corleone (The Godfather Trilogy)Jack Nicholson will be remembered as one of the greatest film actors of all time. He was The Joker in the original Batman movie, Jack Torrance in The Shining, and the eccentric R.P McMurphy in One Flew Over The Cuckoos Nest. But how fantastic would it be if Nicholson could insert into his legendary resumé the role of Michael Corleone in the Godfather Trilogy. Sadly, this dream of many a film buff, never materialized in real life. Nicholson decided that is wasn't the role for him, and declined, in the belief that he was too old to play Corleone, and instead he commited to the 1973 comedy "The Last Detail," (a role which won him an Oscar nomination.) This paved the way for the then unknown Al Pacino to swoop in and play Corleone, a role which consequently kindled his illustrious Hollywood career. Nicholson seems to have few regrets over declining this role and he has publicly stated this: "Al Pacino was great in the part, and when I saw the picture I couldn't see anyone else in it." Clearly very humble words from Nicholson, but perhaps deeply entrenched in his mind is the slight feeling of regret, that he passed on the chance to appear in the most critically acclaimed film trilogy of all time, amongst the likes of equal greats such as Marlon Brando and Robert De Niro.