This question was posed to me recently:

What IT knowledge is most lucrative?  Does it pay more to have J2EE knowledge?  Or ASP.NET?  Or XML/JS/AJAX Web Development?  Or SAP?  Or SQL/RDBMS?

Definitely, one needs to have well rounded background.  Knowing one, and only one, technology will not be helpful. 

But if you are to specialize, which one would you choose?  Of course, with cash in mind.

I don't know the answer.  Do you?