The idea that it lost is that the console did very poorly compared to it's predecessor. Overall, 84 million units and still counting for a console is fan-fucking-tastic. But when you look at it's namesakes that both did 100 million +, one even going as high as 157 million, makes the achievement seem a little less awesome.
You pretty much said it your OP: The PS3 was more of a PR comeback for Sony, rather than a comeback overall.
Now, the people saying XBone is making aren't very bright You can't make a comeback if you were never at the top to begin with. People's minds just function wierd, I guess.