Video Card Performance Reference
Futuremark has one of the best quick reference and comparison web pages for video card benchmarks. You can browse the benchmarks of all the video cards from ATI and Nvidia and compare them. It's a great reference tool when deciding on a new video card. Here is the link.
They provide a simple dropdown list, and although the pick list itself isn't sorted alphabetically (maybe it is sorted by review date), you should be able to find almost every popular desktop video card chipset variation listed.