I don’t think, the current discussion is about Google vs Microsoft competing on the same platform (software). I also agree, that Google doesn’t have a platform (yet).
I think this is about influence. And power. Microsoft was and is gaining influence on software. Products that let you manage/store information. They built a platform, which has reached every desktop PC near you.
Google is gaining influence on leveraging that information. Building a yet to be defined platform. And yes, they finance their endeavours by advertising. But ultimately, it’s about information, their mission statement says that. And, from leveraging information via control to power it’s a short distance. Once they have achieved that, they have a „platform“. It’s disconnected from software, hardware or anything else we define as a platform these days.
It’s about information and control. And it will make all other platforms obsolete, because access to and leveraging of, information is not defined by operating systems like Windows any longer, but by, well, whatever Google will call it…