So there's iTunes (2001-2019, but arguably renamed to Apple Music, so not actually dead), and Ping (2010-2012), the latter of which had approximately three users.
Like for like, Google Play Music (2011-2020) isn't quite as long-lasting, but more to the point, I'm not sure Apple has simultaneously maintained two competing services before ultimately canceling one.
Then the GP commenter mentioned "chat services," which makes the position unassailable. Google seems to have launched and folder a dozen or two chat services over time[1].
0 https://support.apple.com/guide/facetime/welcome/mac
1 no evidence cited
I can FaceTime with people halfway around the world with more clarity than I can talk to someone on the same WiFi network using WhatsApp.
Also, I was on a project with a colleague who had a poor internet connection and we found FT worked better than zoom. FT video quality seems to be the best of the services I’ve used but personally I don’t care about this part much.
I wouldn’t call these “killer features” but they are enough, with the integration into address book etc, to make it flourish.