Shakespeare depicts human beings, not types. How far is this statement relevant to "Julius Caesar" and other plays?
I think that this statement is very relevant to Julius Caesar. Each main character in Caesar is very much an individual well rounded character. You can not easily say Antony was the "good guy" and Brutus was a "bad guy," or even that Caesar himself was a great selfless leader and that Cassius was an evil traitor. Each has good and bad characteristics within him that does not make for easy assignation to types. Brutus was an honorable man who chose to do a dishonorable deed for honorable reasons. Antony appears as a selfless friend until we see him changing Caesar's will and denigrating Lepidus behind his back. Cassius may have been a traitor and a coward, yet he is loyal to Brutus even when Brutus makes choices that bring about the their ruin. Finally Caesar was ambitious, yet he loved the people and wanted the best for him as is seen in his will.
This statement is also certainly relevant to other plays although I do not have time or space to discuss them all here. I would suggest that you look at Hamlet, Lear, and even Macbeth to see the humans that Shakespeare portrayed. I believe his portrayal of humans rather than types is one characteristic that contributes to his universality and has helped his plays transcend time.