how is it that COD4 scores a 10 for graphics and Uncharted only a 9?
Most casual people or reviews don't have that understanding of what is technically demanding in a game (and therefore impressive) and what isn't. On firrst glance, COD4 looks very good with its aim for as much realism as possible, the attention to detail, the lighting, smoke effects etc. It's all very well done. Then you have R&C that's also very beautiful game, because it does what it tries (a cartoony platformer) very well. Then you have Uncharted - a great looking game, but has neither a cartoony style, nor a very realistic one. It's in between, which probably comes across as less impressive from a casual reviewers point of few. I have no doubt though that on a technical level, Uncharted is one of the most impressive games out at the moment.
AC while good looking, but be fighting with lower graphics score due to the tearing and framerate issues. I don't know about you, but even if a game had the most unbelievable graphics, if it couldn't play them at a smooth framerate, I wouldn't be talking of much an achievement. Tried isn't equal to achieved.