Well your not rong to think that the ATI card have the edge but i am afrade that just rather good marketing from there part with the slip up thy made in 2004.
But they were the best by a hugh way in 2003 but let me explain.
Its all to do with the technology built into the cards them self, the ATI cards are sort of on-par with NVIDIA as far as feature are concerned but there just missing the latest shaders for rendering that can be found in games like Black & white 2, Doom 3, Stalker to name a few.
now why do they look like they do so well against NVIDIA is because Half Life 2 is built on a Direct X 7/8 technology but on steroids, so if you are following so far what that means is at this moment in time they look great because all there pixel shaders (graphics technology) is gear to run old technology (direct x 7/8 and bit of 9) very well when NVIDIA on the other hand has built there cards for the future technologies, is why they look so good in games like Doom 3 but not as good in games Like Half Life 2
but your probably thinking so what i won't to play Half Life 2 so I Should go ATI, the answer would be no because ONE big reason the difference is marginal and the Doom 3 engine is Saleable so your going to get lots of games Running on the doom 3 engine over the next 3 years and that not including a little game called Unreal 3 (see picks Below which use the new technology in the NVIDIA cards.
so conclusion is ATI is in a panic and are showing the would what they won't you to see and even copying NVIDIA by bringing SLI solution soon as well because in this aria NVIDIA is more then king it is God him self.
As for cards here are some suggestions (remember I have bow idea what your budget is for a graphics card)
I will get back to you on the cards to choose as i went looking for a good card to choose but there is some crazy stuff going on right now and i will let you now as to what is the best card, sorry.
these are all in game graphics