Is it? That's $240, or 3 launch day AAA games a year, plus a slightly older sale game. Microsoft doesn't publish that many games that people want day one, and you can build a big library of games of all scales relatively quickly if you're willing to spend $240/year on games and are moderately patient with sales/used games. And many of the games people are enthusiastic to buy on launch aren't from Microsoft and aren't available until they've been available at reasonable discounts. I'm not sure how much you save with the annual discount, so maybe that's a little better, but a lot of their library are games you could find used or on sale for $20-30 at some point (or cheaper).
I do personally actually prefer PS's "we're not including our games day one" approach because I think it allows them to properly invest in real single player experiences knowing that more people will actually buy them, but $240/year will buy you a lot of library.