I keep seeing the comment that it is "Lack of games and too high of a price that is hurting the PS3's sales" and while this is true it has an underlying optimizm which is not really realistic ... The assumption is that as the PS3 gains quality games and as the price drops it will see higher sales; this will probably not happen to the level that these people are expecting.
Face it, the PS3 has had several games (which were good enough to sell a lot of systems) released and sales have continued on their steady decline; even people who love the genre and liked the game series were not willing to buy the PS3 at the $600 price.
Even if you assume that the PS3 will soon be $400 this will probably not provide the boost in sales (long term) that people are expecting. The XBox 360 has had problems selling in most regions and a large portion of that is that at $400 it is much more expensive than most consumers have ever bought a gaming system for; consider the bulk of every console's sales have been at $150 to $200.
I'm certain people will mention the waves of people that are willing to spend $600 for Metal Gear Solid, Gran Turismo or Final Fantasy but you have to consider that 75% to 90% of PS2 owners never bought these games and a large portion of those that owned the PS2 version would not buy a system for the game; many games are sold because they are a highly marketed, good game in a popular genre on a platform rather than that people love that particular franchise.