Casablanca, One Flew Over the Cuckoo's Nest, Rear Window, Psycho, Silence of the Lambs, It's a Wonderful Life, To Kill a Mockingbird, Taxi Drive Chinatown, Se7en.. All FANTASTIC films directed by directors who didn't have their own story to tell and decided to work with GREAT writers to make GREAT movies. Do you think they are any less Satisfied with those movies because they never wrote them? Would you say David Fincher is lacking in creativity?
<font size="2" face="Verdana, Helvetica, sans-serif">No offence to this guy, but the people you have mentioned (Scorsese, Hitch, Milos Forman, Polanksi) were renowned for being great directors of their times.

And how did they get there? Many of them by writing their own scripts. Anyone whp's seen 'Who's That Knocking At My Door' will agree it's no masterpiece, but it was enough to get Scorsese recognised, enough that he was able (with a friend, Jay Cocks) to get funding for Mean Streets.

You must know a fellow-minded person. Write a script with them.

Also, Fincher is not lacking in creativity. His creativity is visual, whereas other Directors have a falir for storytelling. Whilst the Alien 3 script is shit, you could argue that Fincher's uncompromising style made it go from a two-star movie to a three-star movie.