First off, welcome to the forums...
Second, maybe it's you who don't get it (along with several others...)
Looking at gaming since 1977, EVERY generation of consoles have been a whole new ball game from the previous one. You can always compare successes and failures from one gen to the next, but each new generation can never depend on the successes of the last generation when you look at Atari, Nintendo, and to a lesser extent SONY since each new generation has always offered a signifigant difference from the previous one. Also, the only consistancy in the console market until this generation is that CONTENT IS KING. The Xbox 360 has the most content. But hardwarewise the Wii has already surpassed it in sales, and the PS3 has been erradicating the 360's 10 million units shipped lead with the PS3 still having aces up its sleeves. Because the "CONTENT IS KING" concept doesn't apply to this gen so far, it's safe to say that the only single consistancy has been trounced by lower prices (Wii) thus supporting that each new generation has something relatively new to offer where last generation CANNOT be heavily depended on. And even you said...
"The PS3 outselling the Xbox 360 is no accomplishment by any means..."
So doesn't the above quoted statement also implies that the 360 didn't win??? If it's of "no accomplishment" that means that the 360 is in worse position than the PS3. Your statement is either subjectively faulty logic or outright biased fanboyism/fangirlism. Take your pick. And what does...
"It was always 'supposed to'" suppose to mean??? Is this suppose to mean that both SONY and Microsoft joined together to plan this from the start? Is this suppose to mean that the Xbox 360 was doomed to be beaten by the PS3 rom the start, still implying that the 360 ALSO didn't win this generation? Or is this suppose to mean that you cannot take the fact that there is still demand for the PS3??? The PS3 is in last place, BUT it ISN'T in dead last. Consumers still want that the PS3, there is still sufficent demand for it, 3rd parties are still supporting it some using it as a lead developing platform, it still has its share of 3rd party exclusives, and SONY is pushing both their old and new IP's for the system. In a lot of ways ALL systems have won this generation as well as the PS3 which also allow gamers to win as well.
"Y cant people get it??"
Perhaps the real question is, "Is Sony doing well this generation compared to last?" The answer is obviously no. They dominated last generation, but are struggling to get into a distant second this generation.
Does this mean they will not dominate next generation? No. They just don't have a chance to do it this generation.
They've fallen far, but I wouldn't count them out. They're just no longer the company with the "must-have" console, now.