Firefox, Google Chrome (combined 43% of market share) and Apache (58% of server market) seems to disagree with you.
You are misunderstanding how software works, though.
The operating system and the software you run on it have nothing to do with each other. You can use proprietary software on linux (I own Quake wars and Prey f.x.) and you can use open source software on windows (firefox f.x.)
Take two people with no previous computer experience and sit one in front of a linux machine, and one in front of a windows machine. I'll guarantee there'll be no difference in their ability to do their daily stuff. Why would there? Either way, you are just clicking on icons.
Windows is familiar because you've already used it, not because there's somehow anything more intuitive or helpful about it. (if you don't believe me, google "windows troubleshooting" or similar and see how many millions of hits you get.
Will linux ever "rule" the desktop ?
No more than amiga ever would have ruled it.
Does it matter ?
No. The choice is there for those who want it (stability, freedom). The desktop is only one tiny bit of what linux is, can and does.
Firstly, I didnt say always in regards to open source software. There are examples (as you've given) when open source software is used as heavily as commercial efforts, I have no trouble admitting that and never said otherwise. Predominantely relying on open source and having access to are pretty different things though. As for me not understanding how software works,.... after 30 years of being into computers and developing I think I have a pretty good handle on it. Thanks anyway. Additionally I did say that I know Linux gaming is on the up, and I even mentioned things like WINE to be able to play commercial Windows software, but performance isnt what it is on Windows a lot of the time (as I already said as well). Also,... my post was ripe with me suggesting it doesnt matter to me anyway. I simply stated some reasons why Windows is a lot more dominant on the desktop than linux and why linux has little chance of making headway.
Seriously, did you even read my post, or just skimp through it and try to find fault ? Most of the things you've bought up I addressed already in my post, and both sides of the coin.