Ok, let me see if i can phrase this in a way that wont get me bashed.
The 360 is a Scion tC. A nice car, does everyone one man needs. While its not the fastest, sportiest, or smoothest ride, its a car. Its dependable, goes A-B with no trouble, and doesnt cost you a lot. Leather seats, Power windows, and a good sound system means its got everything you will NEED in a car, but nothing more. This is a 20,000$ car brand new. ((a little more after tax))
Now the PS3 is a Cadillac STS. A far smoother ride, far more horsepower, a lot more sporty, and it can get you from A-B in style. Its slightly more fuel efficient, has all the trimmings both interior and exterior, and is all around just better then the Scion. Everything you want in a car and more. But this car is 50,000$ brand new. ((a little more after tax))
While the PS3 is slightly better then the 360 in all respects (except download, install, and loading times), its also more expensive. And as such, the audience for it will be smaller. Because you have the people who dont really give a sh*t about how good a game looks, so long as it runs smoothly (im in that group), and then you have the people who want their games to look their best.
The big problem comes in when, if you want your games to look their best and play their best, you are more likely going to be a PC gamer then. A PC can out perform both the 360 and the PS3, and do far more then either.
In short, the PS3 is behind because its Better then the worse, but no where near the Best. A Scion isnt a Cadillac, but a Cadillac isnt half a Viper. The PS3 falls into the middle ground where "Give no f*cks" and "Give lots of fucks" collide, and it happens to have the smallest market because of it. Its Advanced, but Behind. Its Better, but Worse. Its got free internet, but if you have disposable income to spend on gaming, 60$ a year is probably very little to begin with.(I mean, you can put 25c into a glass jar everyday and come up with enough cash for XBL.)