Just want to point out that exclusives, unless it's on a Nintendo platform, are usually not the biggest sellers and people generally play multiplats, that being said, for less casual gamers, exclusives do matter, you want to be able to play more games after spending a few hundred bucks.
And Microsoft just took too long to start making their next-gen games, which will bite them in the ass, you'd think being a distant third would have meant that the new console would come out with a new Halo, Forza and something new such as Everwild...nope, those will take a while.
Also, even if multiplats still sell a lot, it's hard to deny that franchises like Uncharted, God Of War and Ratchet and Clank don't make people buy a Playstation console, Microsoft has tried starting some franchises other than Halo/Forza/Gears but they failed, who here remembers Kameo, or Blinx, or Viva Pinata?
Heck, by the time they entered the market, the Playstation had already been a huge hit and several big franchises had already started there such as Resident Evil and Persona(though this one got big after the PS1) and had gotten big iconic games like FF7 and Metal Gear Solid in it, and Final Fantasy amongst many japanese games still only went to PS2.
Look, i don't really hate the Xbox, and i do wish it was a bigger competition to Nintendo and Playstation, but Microsoft only got some real momentum with the 360 and that failed because of serious hardware issues, and the Xbox One launch was TERRIBLE.