I have tryed many i here what i think:
Geforce 2 MX 440 - Extremely good in its time but nothing by todays standards .
Geforce 4 MX440 - amazing in Direct x 8.1 but in games like far cry it stands no chance
Geforce 4 ti - Probally the best card i ever had its amazing it played all games full settings up til far cry came out.
Geforce 5200 - Dont go there get a geforce 4 ti if ya can find one .( no offence to anyone who has one ) its good for everyday pc user but not gaming
Geforce 5600 - Same really a gloryifed 5200 in far cry the geforce 4 ti beats its for frames and detail .
5900 - Totally amazing this card is head and sholder above any of ati offerings at the time we are talking high setting in far cry at around 30 fps or medium to high @ 60fps.
6800 Ultra = Its totaly amazing if you have money to burn get it but go for a 6800gt if you dont want to spend 400 quid .
6800 GT = the best nvidia has ever done its just a tad less powerful in the benchs and games but we are talking 4 - 7 fps which when you getting 60 - 100 fps you wont notice . So this is the best card of this gen . and the 5900 and 5950 are the best of last gen.
Hope that helped it was fun to write anymore questions just ask.