I'm sorry but I really don't consider Microsoft a game maker at all. If anything, they just buy out other companies.
Buying companies that have already done the groundwork for things is an extremely well accepted practice and common end goal of startups with the "enter into an exclusive deal" type arrangement being not that far behind. Add in mergers and you have another.
Pick any big company (especially in games) and they will probably have a long list of these sorts of things to their name.
Beyond that Microsoft have developed serious game playing tech (directX and XNA to name but two). By all means think as such but it seems a rather odd line to draw and one that excludes an awful lot of companies most would recognise as companies that have their primary business and/or a serious component thereof in the games world.









