I'm not going to assume what games both companies will have at launce. What I will say is I don't remember Sony having a heavy hitter for the launch of the PS4 and it didn't matter in the end. So again, putting so much emphasis on Microsoft's decision to go cross platform compatible is being blown out of proportion. We know these systems start taking strides around year 2.
This is generally ignorant of even basic recent console history.
Acting as if every launch exclusive is Knack-tier is already daft (the Switch just launched ffs), but it also misunderstands why launch exclusives exist at all.
The PS4-XB1 launches had plenty of titles to sell people on the concept of next-gen, which is where the Series X will most suffer.
Killzone Shadowfall quality is less important than the fact it looked better than anything else at the time. Next-gen is here.
This helps sell consoles irrespective of quality.
More recently, BotW worked to convince people the Switch could handle big, complex open worlds, and AAA level quality, something the WiiU famously failed to do. The launch quality is a cherry on top.
Besides, MS's approach doesn't benefit quality in the slightest.
Launch devs still have to deliver visually impressive titles, just with an extra platform to support on top.
This will lead to hamstrung next-gen games, with poorly running current gen versions.
Let's compare:
A MS first-party studio will have to support 6 SKUs: XB1, XB1S, X1X, Lockhart, Series X and PC
A Sony/Nintendo first-party? 1, either PS5 or Switch