Anandtech has a pretty good table for comparing the performance of the 3870/8800GT at different resolutions (bottom of the page): http://www.anandtech.com/video/showdoc.aspx?i=3151&p=6
The 3870 offers between 83% and 87.5% the performance of a 8800GT. So if you are choosing your next card based on price/performance you can see if the relative prices make sense.
The 3870 offers between 83% and 87.5% the performance of a 8800GT. So if you are choosing your next card based on price/performance you can see if the relative prices make sense.