If anybody doubts why Patrick Stewart deserves this, just remember the awful scripts of the first seasons of Star Trek: The Next Generation and how Stewart gave them some legitimacy. Once the scripts started getting good, he was already there.
It leads to the old question of who you would prefer in command of an emergency, Kirk or Picard? I've always said it depended on the situation. In battle, my choice is Kirk. However, in a case of diplomacy, Picard would win hands-down. And I say that because of Stewart's incredible acting presence.
His one-man performance of Charles Dickens' A Christmas Carol was absolutely superb. He kept up an amazing level of energy for over an hour and a half with no outside assistance whatsoever.
Congratulations, Sir Patrick. This is an accolade well deserved.