Why do you think this speech has become so famous? has king dream been realized? why or why not?

The speech has probably become so famous because of the rhetorical devices King uses to make the speech memorable and effective. Repetition especially contributes to this. "I have a dream" as a statement has become representative of the whole movement, because he repeated it so many times and it was fueled with such passion. 

King's dream has been somewhat realized, because there is legal equality in the country. However, there are still people who are struggling and still people who are prejudiced, so it has not been fully realized across all people.