Where a console rates on the all-time sales leader board is pretty irrelevant, since the industry has grown so much in absolute terms. As when looking at movie box office revenue, you need to look at more than one number if you want to judge the real performance of a console in the market.
Here is a good example: The PS3 sold only slightly more than half as many units as its predecessor, the PS2, did. Most businesses would, in fact, consider it a failure if their 3rd generation product sold much more poorly than the second generation. Sony's rapid move away from the PS3/Cell architecture gives you a pretty good reason to believe they considered it a failure too.
Here is a good example: The PS3 sold only slightly more than half as many units as its predecessor, the PS2, did. Most businesses would, in fact, consider it a failure if their 3rd generation product sold much more poorly than the second generation. Sony's rapid move away from the PS3/Cell architecture gives you a pretty good reason to believe they considered it a failure too.