Honestly can't predict it. Too many games coming out at launch to choose from, will entirely depend on my mood and other conditions like:
Are my friends over and is my brother there?
If that's the case, then that decreases the chances of the first game being a single player one, unless of course they want to see a demo of what the system can do (in which case it'll probably be Killzone)
I will say this, even though it is a local multiplayer game, even if 10 friends are over (and want to play), no way in hell is COD going to be the first game I put into the PS4.