Sales, something like 40 million ps2s were sold after ps3 came out. I might be wrong on that number as it's possibly a lot more, but there are several reasons why it is important.
1. Brand strength: Coming out on top will be a significant mental victory that could help consumers tie the brand to strength and longevity.
2. The stronger sales remain, the better the chance sony has at recouperating losses incurred earlier, additionally, it helps with both the emerging markets introductions to ps3, and will help defer costs of any loss leading ps4 sales.
3 The more games ps3 can continue to grab, the better they will be able to push that backwards compatibility peripheral we've been hearing about for ps4.
4. The more consoles they sell, the higher the game sales.
5. The higher the discrepancy between sales, the greater the cascading effect of it. Beating 360 might actually create more sales AND will be a strong media blitz (free advertising).
