Not to compliment myself or anything, but I honestly felt like the Xbox was in trouble as early as 3 years back. Not coincidentally, this is when I switched from 360 to PS3. Sony was slowly building up a small fleet of must have exclusives, and PSN was starting to build parity in features with the more expensive Xbox Live. Microsoft was losing each E3 for years, with very little to show the core audience besides Kinectimals, Nike App, and ESPN. They were promoting timed Call of Duty DLC as some of their centerpiece content instead of exclusive games. Then they raised the price of Live instead of lowering it like many predicted as Sony caught up.
That's when I switched. After that, we got PS+ and the instant game collection, which blows Live out of the water.
The defense from a lot of 360 fans was that surely the 360's last 4 years were slow on exclusives because MS was gearing up behind the scenes for a very aggressive launch window. This honestly made sense, because they did this with 360. But when none of that showed up, the true extent of their mismanagement became evident.
I honestly thought Sony was outperforming MS on content for years prior to PS4's unveiling, and they were offering better value. But I never expected MS to bungle things as much as they did. A lot of the warning signs were evident though, years in advance. This didn't happen overnight. They changed their focus from games and the core audience to pursuing multi-media and the casual audience. And that's when I left, and it was 3-4 years ago.