Now that I think of it, the list of under and wrongly used African Americans in films is HUGE.

I'd have to include James Earl Jones as wrongly used in films, especially in those sentimental African American feel good crap films he's been forced to make to keep working. And the list of African American actresses who are excellent, but under-used is astounding.
Esther Rolle did a whole lot more than her most famous TV roles on 'Maude' (she was a scene stealer!) and 'Good Times' (ruined by that jackass kid, but remember, she played opposite John Amos, an excellent actor) She had a much better stage career.

Angela Bassett trained at Yale Drama, just like Streep, and excoriated Halle Berry for taking the role that won Berry the Academy Award in what I thought was a really racist film. I love that Angela!

Cicely Tyson.

One of my favorite American actresses, Alfre Woodard. It's no coincidence that two out of the four women I just mentioned have made it into John Sayles' films...

Some African American actors who ought to be on the same level as Jimmy Stewart and Robert Mitchum: Ossie Davis, Laurence Fishburn, Gregory Hines (amazingly good actor for a dancer!), Paul Winfield, and the two most misused actors ever, Sidney Poitier (in dramatic roles) and Richard Pryor (in comedic roles).