They could be right or not, but boasting about it is kinda dumb.
Regardless, I personally don't trust Microsoft to provide good exclusives during the entirety of the console's life. I look at the 360 and I see that they provided a lot of good exclusives early on, but then they stopped and all we were getting was Halo, Gears (which is a 3rd party, as far as I know) and Forza.
Meanwhile, while we were getting these 3, Sony had Uncharted, inFamous, Tokyo Jungle, Wipeout, The Last of Us, etc.
So yeah, I don't trust Microsoft to have good exclusives because of that. The 360 at first looked like they were really trying to provide many exclusive games, even exclusive games by Japanese developers, but then it stopped, as I mentioned. Hell, some 360 exclusives even ended up becoming multi-platform, like Mass Effect. That's another thing, too: most games are developed by 3rd parties and 3rd parties definitely prefer to go multi-platform than exclusive.