If a good game achieves sales that can make enough money to warrant a sequel, I'm fine with that. Examples of these are Resistance, Killzone and Infamous. They may not sell many systems, but they are quality games and there is a big enough market for them to make at least make money. This isn't a huge problem for SONY because they do have other IPs that do very well and sell systems. E.g Uncharted or Gran Turismo.
Twisted Metal is a complete failure everywhere apart from NA. But why should we care if it makes money and gives the niche it appeals to what they want. It was never meant to sell systems, I'm sure SONY will be very happy if it only does 500k and 95% of those sales come from NA. They don't need it, it doesn't matter.
To give a direct reply to "So can we still say that Sony games don't sell on Sony systems?"
No. What we can say is some games don't, some games do. The games that do are Uncharted, GT and to a lesser extent GOW, LBP and MGS.
