The unfortunate reason behind the PS3's lack of sales is due to the high price tag, despite it's extreme value that everyone seems to completely ignore, but if you take a look here...
The PS3 hardware itself, just to play PS3 games = about $400.
The blu-ray player embedded in it = Says HMS, about $1000 alone.
The hard drive = Around $150.
+ the controller that comes in the package = another $60.
The current prices of the PS3 went down recently, so let's take a look at this, in American prices:
$399 for the 60 GB hard drive version.
$499 for the 80 GB hard drive version + you get motorstorm bundled with it, which is worth another $60.
If you add this up... you're getting one hell of a deal. It is undeniable that the PS3 is the best in terms of the features it offers, whether you like it or not. However, because it's a lot of good things packed into one machine, the first idea that manifests in people's minds are "OMG XPENSIV", which is not fair.
Secondly, one of the biggest complaints against the PS3 right now are that it only focuses on graphics. For one, this is a subjective matter on whether or not you enjoy good graphics, whereas all I've done so far is give factual information about it's specifications. Secondly, the PS3 only enables advanced graphics for the games from the game companies. When was the last time you saw a game with terrible graphics and amazing gameplay? Grand Theft Auto is probably the only exception. This is a viewpoint that is basically uninformed and biased.
The PS3 is an unfortunate scapegoat of the general community and hated on based purely on its pricing.