What makes Shakespeare such a great writer?

Here's what: People have been standing in line for 400 years to see his plays. 

From yesterday's NYTimes:

The current Shakespeare boom on Broadway is not unprecedented and hardly limited to that most prominent corner of the theater world. Every summer, our parks are overrun with star-crossed lovers and introspective Danes. America is glutted with Shakespeare festivals and theaters. In a 2010 post, the theater blogger Isaac Butler called this our “Shakespeare problem,” tabulating over a thousand Shakespeare productions at nonprofit theaters in the first decade of this century.

[Emphasis mine.]

The play's the thing.