I'm afraid this question is too big and too open-ended to really address in this format. Johnson was one of Shakespeare's contemporaries, and wrote a number of plays. He's best known for his comedies, which tended to be pretty dark and cynical about humanity. I'm most fond of Volpone, but others consider The Alchemist to be his best play. He also wrote masques for the court (allegories and elaborate shows using expensive designs, music, and dance). To really examine him as a dramatist, you'd need to read one or more of the comedies and one or more masques, such as The Mask of Blackness. You'd then want to compare their qualities and analyze similarities, differences, etc.

Greg