Funzo6785

I was just wondering, if anyone knows, why are Half-Life 2 and Doom 3, from what I understand two of the three best looking games out there, powered by two different components mainly.(This probably doesn't make sense, read on) For example, I saw a post that said if you have a Athlon 64 3700+ and a NVIDIA 6800 Ultra running DOom 3 on top settings, You would get 65-80 FPS. Then it said that you could downgrade to say a 2500+ and only lose 10-15 FPS, where as you could redo the exact same scenario with Half Life 2, and downgrading the proccesor would render it almost unplayable. And same case with Half Life 2. I heard you could go from a 6800 Ultra to a NVIDIA 5700FX and still run it on near top settings so long as you have a top of the line proccesor powering it, where as you could do the exact same thing with DOom 3, and it would be rendered almost unplayable. If anyone knows that would be great, I'm just curious.