Personally speaking the first PS4 game I really want to play is Infamous Second Son.
We all know that the next gen party truly begins next year while this year at launch, as OP rightly pointed out, we'll get mostly PC ports of games not truly conceived for the new hardware (Assassin's Creed, the new Call of Duty, Battlefield 4, Watch Dogs).
And I also agree that with games like GTAV, Beyond, GT6 and Castlevania Lord of Shadows 2 coming out in the upcoming months on PS3, I could easily decide to delay the purchase of the PS4 until Infamous is released in February/March next year.
While I'm sure that there will be exciting announcement at Gamescom and TGS I think that none of them will be about other launch titles (with the possible exceptions of a few japanese titles like a new Hot Shot Golf, a new Dinasty Warriors and things like that, if the PS4 is launching in Japan this year).
So yeah, being rational I could really well wait until next year.
But even if I skip the launch, I know it will be really hard to resist not to get it as a Christmas gift and also this console won't get a price drop for at least a full year, so it's not like delaying the purchase will give me any benefit if I can afford one later this year.
At this point it's better to enjoy the system from the beginning LOL
