Well many of the first movie "shorts" were white actors in blackface. I don't know the first black actor to appear in an actual Hollywood feature film. Try this link for more on that.
http://members.tripod.com/Moochie_Peguese/black_film_1.html
While Poitier opened the door for actors and actresses I think the field has yet to be truly expanded in terms of recognition for directors, producers, screenwriters and the like.
The professional struggles of rising black actors and actresses over the years can only be surpassed by their personal struggles within society as a whole. I think most of the time black entertainers were considered talented in the sense that they could perform on stage or on film only because they had been scripted to do so. To rise above the written page and grasp the true nature of the character one is imitating and then have the audience realize the actor or actress has reached fruition with their performance is to truly have acheived perfection within a role.