Why does it seem that all the great clical composers are dead?

I can't think of any great composer who is still alive. Is it that they are only really recognized as being great after they die, or is there just a current lack of really great clical composers around today? If you disagree who do you consider as a great composer to compare with the Mozart, Beethoven, Schubert, Bizet, Puccini, Verdi, Tschaikovski, Bach etc.