It's definitely a success, but:

* Its success would not save Microsoft if Windows and Office usage sharply declines

* Nor would its failure ever break Microsoft

* ...both of which resulting from the market being not very large by Microsoft's standards

* I'm not so sure about this last one, but a competitor could come out with new exciting hardware at any moment (a recent example is VR headsets) and then gamers would flock to the new platforms and so would game developers. Since people care less about old titles, the barrier to entry is not nearly as high as in the Windows or Office cases.

That said, my case is shaky enough, and I wager that you could find counter-examples that would make the Xbox omission tiny in comparison :) I just had this thought and was surprised by how many companies sorta fit the pattern.

Last I checked the XBox was still a net loss for MS. Ed: http://www.neowin.net/news/report-microsofts-xbox-division-h.... The numbers look really bad if you look at opportunity cost. And long term things are not so hot as they still don't own the market with the PS4 selling significantly faster. http://www.extremetech.com/gaming/187371-ps4-outselling-the-...

However they sold a wide range of peripherals (mice, keyboard, etc) which was profitable just not a significant impact on their bottom line.

Or the intellimouse.