Black & White 2
Focusing specifically on the impact high-quality settings have on frame rates allows one to determine each card's maximum "playable" quality level. We begin with Black & White 2, using the default medium settings, then the maximum settings plus 4x anti-aliasing (AA-High).
The X1950XTX appears to be the minimum card needed to play Black & White 2 at high resolutions and quality. Buyers on tight budgets will find adequate performance from the X1900GT at high quality and medium resolutions, but 7600GT might want to upgrade.
In Fear, we chose Maximum System/Medium Graphics as a base line, moving up to Maximum Graphics (4xAA/16xAF with Soft Shadows enabled) for the quality/performance comparison.
All three cards can play at maximum quality up to 1280x960 in FEAR, but the 7600GT drops out of the race at 1600x1200 pixels.