I am building a PC around christmas time for about $500. It will have 2gb ddr2 and amd 5200+. Because of my budget, these are the only two cards I am considering. I would be playing crysis and COD4 and bioshock and alot of new games. I wouldn't do any overclocking and I'd be playing at 1440x900
Start here, read this. http://www.tomshardware.com/2007/12/03/best_graphics_ca...
The 3850 is a better VALUE. If your budget is tight, I suggest this card.
The 8800gt is slightly FASTER.
Many will say ATI has better picture quality, I would tend to agree with them that ATI cards do generally have a better picture quality than nVidia cards.
Against these 2 choices, it's mostly personal preference.