I'll probably get a lot of flack for this, but I would suggest Knack and Killzone. Not only are they true exclusives that you can't play on anything else, but they're pretty solid games.
For reasons that are incomprehensible to me, Knack instantly got bad feedback from the a large majority of the gaming community despite it being a great game. The game has no glitches, has a wonderful art style, solid voice acting, good platforming, and good gameplay. People seemed to write it off immediately because it "looked stupid/kiddy" and "was too easy". Not only is that hugely subjective (the game is rather difficult if you play on Hard without any bonuses), but Nintendo gets praised for doing exactly the same thing. /boggle I platinum'ed Knack around launch, and I enjoyed the game thoroughly.
Killzone was the same way. Somehow Ghosts reviewed better despite Killzone having a longer, better single player campaign and a multiplayer that was just as good. And it looks fantastic to boot.
I bought both of these game for full price at launch, played them to death, and enjoyed them both. If you are just getting settled with a PS4, I see no reason to ignore them; especially if you can pick them up for $30 each, brand new.