The architectural differences that made a console more compelling than a standalone PC are largely gone. (Nintendo is a bit of an exception here, but they were always playing a different market than Sony and MS anyway)

This means it's harder and harder to say "here's a unique experience you only get on Xbox" (or Playstation for that matter)

The price advantage is going away fast, especially with talk that next-gen consoles will top USD 1000.

All they have left is their prestige first-party products, which they don't seem to really know how to use effectively. Some of them have solid cultural penetration, and could spawn broader media franchises with the right handling.