*sigh* It looks dated because it is dated. It's the same X-Ray engine (with a few tweaks) that was used in the original.
The extra 'ugliness' also stems from the fact that you are using DX9 - Use DX10.
Screenshots don't do the game justice as the dynamic weather/lighting effects/etc are impressive. TBH, the hue and cry of it being 'ugly' is overrated.
It still doesn't utilize more than one core effectively, but setting the affinity on xrEngine.exe manually in Task Manager does help with the jerkiness.
Yes, it's poorly optimized - but what STALKER hasn't been?
Basically, despite having to dial a few settings down here and there, it can be rendered playable. Bugwise, it's the most stable 'out of the box' STALKER releases.
Just because your machine 'has met it's match' doesn't mean it's a game 'not worth buying'.
Welcome to the world of IQ sacrifice vs Playability
Metro 2033 will be different as it's not an 'open-world' game which means it should perform better and look better, (ostensibly due to better resource allocations owing to the smaller map sizes / less A.I etc)
Although the lack of PhysX on ATI cards will having many complaining it looks ugly as well...