Ultimate Nick Fury is a reinterpretation of the classic Marvel character Nick Fury. One of the most notable differences between the two is the fact that Classic Fury is a Caucasian colonel with brown hair, while Ultimate Fury is a bald African-American general, and was in fact specifically tailored after actor Samuel L. Jackson with his permission.
The Diva (Interviewer): Did you know that your likeness is being used for the character of Nick Fury?
The Man (Samuel L. Jackson): Yeah I know. We talked about it. It’s cool.
It is very clear that the Ultimate Nick Fury was based on Samuel L Jackson. I can't find anywhere that indicates that this was in preparation for Iron Man the movie, but it really makes me think they have planned on using him for a long time.