Hey jakal, you know that all three movies you mentioned came out in the same year!? 1967! Besides the ones you mentioned, he was in some other important films.
"Blackboard Jungle", "Edge of the City" and "The Defiant Ones" were all important 50s social-problem films involving race or juvenile delinquency (Poitier and the other students were about 10 years too old to play high schoolers in "Jungle", but let's try to forget that.)
In the 60s, of course, he was charming (enough to win an Oscar), playing the handyman who builds a chapel for German nuns in the Arizona desert in "Lilies of the Field." He was also in a nuclear nightmare thriller, "The Bedford Incident", which I'll recommend. "A Raisin in the Sun" stands out as an important play and film in its depiction of African-American life.
My favorite Poitier film of the 70s has to be "The Wilby Conspiracy" where Poitier plays an African political activist who gets unwitting help from Michael Caine while being chased by Nicol Williamson and the law. It's both exciting and funny.
There's more to discuss, but I'll pipe down for now.
"Naked Woman, Naked Man
Where did you get that nice sun tan?"