Sales and quality don't always equate, just like a lot of pop songs and big budget crash grab flicks and quality dont equate to classics. A game that has interesting characters is well built on a firm foundation but has accessibility for everyone will sell well. Your chances of that being a console shifter becomes even greater. Killzone is an inaccessible game for most to play, KZ2's controls were not suitable for a wider audience like Halo. It was more realistic, focusing on the weight of the weapon. Halo's gameplay style influenced games like COD which is why those two games run the FPS market. It's got great characters, fun maps and missions, great ways to play with your friends. This is what truly makes playing FPS on the Xbox 360 shine. Sony hasn't fully grasped this yet, but then again they excel at everything else compared to Microsoft. Sony's marketing is also a huge issue. Microsofts marketing is just godly.