Wow, that sucks. They should acquire someone with a bigger catalogue!
And Obsidian Entertainment. And inXile.
You could see it coming that this is controversial.
1. Microsofts share in publishing video games isn't exactly what you'd call small. They acquired Zenimax Media [1] last year, which is kind of big. That said, Microsoft can't be seen as a dominator in the publishing market.
2. But the argument wasn't necessarily about who owns the most studios. Microsoft absolutely dominates in the platform market on PC. Games are developed for Windows. Period. Everything else is either niche or an extra.
1) Microsoft holds a very respectable share of the video game market (especially if you ignore mobile). But their share of the PC game market specifically is much smaller.
2) Microsoft is the dominant platform of PC gaming without question. But that doesn't make the market attached to them. Being without alternative or having high switching costs is what makes you attached, not merely using it. Most games are inherently multi-platform, either because they are built in an engine that is or because they are also sold on other platforms (mostly consoles). Not having Linux, Mac or SteamOS builds is usually a business decision, not a technical one. You could argue that they are attached to Microsoft because that's where the consumers are, and that's true in a sense. But that limits what kind of benefit Microsoft can get out of the attachment and what kind of damage they can do - at most as much as it takes to get enough consumers to switch (dual boot, some SteamOS device, etc). In a world where games sell platforms the attachment isn't very strong
PC Gaming runs on Windows, not on Valve's OS (while valve is intending to change that progressively).
It's not like you have to pay royalties to Microsoft if you sell a PC game (but you do have to pay MS/Sony if it's a Xbox/PS game).
In what way is PC gaming attached to Microsoft? Microsoft Game Studios doesn't have a lot of market share in PC games besides Minecraft, and the industry is very diverse. Most games happen to run on Windows, but apart from DirectX they have resisted every attempt from Microsoft to use that in any way.
If PC gaming is attached to anyone it's Valve, but even that is slowly changing.