Microsoft still hasn't made one red cent on video games. The cost of them "doing well in the market" is somewhere between $6 and $8 billion dollars. They've only had 3 or 4 out of 27 or so quarters actually be profitable, compared to Sony's consistent (until recently) profit and Nintendo's RECORD profits.
Think of it this way, imagine a woman hacking her face to pieces through plastic surgery in order to look better than a slightly aging beautiful actress and a young beauty queen. She may end up with comparable looks, but she's killing herself doing it, and those scars will have to heal later. Imagine if Microsoft does wrest control of the market. They'll have to make up those billions somehow, and they're already charging more for games this gen.
Microsoft APPEARS to be doing well, but under the surface it's a different story, no matter how many games get a 9.0 from enthusiast press sites. The attach rate is impressive, but consider that total games sales will remain under the N64's, due to the complete lack of appeal in Japan and limited appeal in Europe. I don't seem to remember the press writing many congratulatory editorials for the N64, do you?
They appear to have met the threshold for outright purchasing marketshare at the cost of their own blood, and it appears to be a stagnant figure.