Xbox 360 was beating the PlayStation 3 in sales until late in the generation and by the PS4 and Xbox One the PS3 had slightly outsold the Xbox 360.

It's easy to explain how PS2 beat original Xbox since PS2 had DVD support out of the box and PlayStation was already established due to the previous generation. Xbox 360 did well for them to be beating PS3 but as PS3 games started outputting more the console jumped in sales. The Xbox One launch was lackluster and PlayStation 4 was simply cheaper and more powerful so it started with a lead and is around 2:1 in terms of outselling Xbox One.

So I think PlayStation just had a larger marketshare overall and always had because Xbox came into the market at the height of PlayStation domination.