It seems rather contradictory to be set on buying one system for the gen, and to do so based on launch games. Not least of which because these systems will ultimately share the vast majority of their titles.
I'm sure it will cause umbrage to say this, but I imagine if one who says "I'm getting a PS4 because Killzone." or "Xbox One because Forza." really introspectively reflects on their purchase intent the underlying reality is more "I'm getting a PS4/Xbox One because that's the system I've chosen/brand I prefer and Killzone/Forza happens to be on it." for a lot of people.
That's what I'm saying all the time, yeah. I think so too.