You can't buy a compnay if they not selling. If Microsoft was to do it, it would mean a lot of change in the companies. People would get fired and some would quit and go work for another company. That would make sales low for games like madden which is the best selling series for EA. I'm not going to buy a xbox just to play EA games.
Also it wouldn't end the war cause Sony can do the same thing by buying other companies.