With how the PS3 has performed so far, it will be a miracle if the PS3 is not considered a failure (or a stumble if you'd prefer). Realistically, Sony has a pretty tough battle ahead in order to become profitable on the generation, to not lose a ton of third party support, to sell to 1/3 of PS2 owners, and to not come in third place.
Certainly, the PS3 will have performed better than most when it comes to raw sales numbers (and to a lesser extent marketshare) but on its own this is a pretty hollow measure; the only company which has fallen as far as Sony will (probably) fall in this generation is Nintendo, and it took Nintendo 3 successive generation of constantly increasing competition to fall that far.
I don't want people to misunderstand what I am saying to mean that the PS3 is selling at an awful rate. I do think it is important to look at a consoles performance in context with the previous systems to determine whether it was successful or not; as an example, even though the XBox 360 and PS3 may end up selling at a similar level (roughly 40 Million) I would consider the XBox 360 successful whereas the PS3 would be a failure because the XBox 360 would represent growth in userbase size as well as marketshare.
