Compare the first four months of the PS4 to the first four months of other consoles. Its arguably one of the best machines to ever come out.
Indeed, which makes it all the more impressive that X1's launch lineup was even better than that, with multiple high budget, AAA franchise titles at launch.
That said, I actually think that Sony's got a very fine library of games, given this stage of their lifecycle with the console. Games are bigger than ever, more complicated than ever, and more difficult than ever before (which makes them more expensive than ever to make), so having the kind of quantity of quality content on both consoles at this point in their life is actually really, really impressive... and I just happen to think MS's suite of games is even more impressive... but that's not directly relevant to this thread.