Comparing PS2 to PS3 makes little sense.
PS2 launched first, had a decent price, sold 15Million+ WW (5 Million+ in each region) before there was any competition. It offered an inexpensive DVD player right when that market exploded. And by the time the GC and XBox launched the PS2 has all the third party support it would ever need.
The PS3 launched second, a year behind the 360 (and even worse in Europe). They have a horrible price. Not to mention that the 360 can produce similar graphics while the Wii can do things neither of the other 2 can.
So now Sony is losing money on each system, a lot of money. At any moment MS can stick it to them with a $100 price drop. The Wii is profitable now and outselling them by a huge margin and is priced for mass appeal.
The bottom line is this:
Sony over estimated how many people wanted BD right now.
Sony over estimated how many people would pay $600 for a console.
Sony over estimated how many people would buy the system w/o any games.
Sony under estimated MS and let them get a head start with similar specs.
Sony under estimated Nintendo and just got blindsided (as did MS).
Any game that has released so far that was going to change the momentum has failed to do so. Just like no game magically saved the GC, I think PS3 is in the same boat. They will have some great games, but they will never be the market leader this gen. Luckily MS is screwing up too so they have a chance for a distant second place.
When Lair and some other AAA games come out and PS3 is still getting crushed by Wii, then I think more people will start to admit the obvious.
The final marker will be this holiday. If the Wii, and 360 pull further ahead then it is over. You will start to see less and less sales, and more 3rd parties leaving.