A CPU's performance is usually determined by it's architecture (16-bit, 32-bit, 64-bit, etc.), the number of cores and it's frequency.
What would be the equivalent for graphics-cards? I've always wondered since most games state requirements like "Like XYZ or better", but how can I know how "good" XYZ is? Only by it's price?
Note: I know about benchmarking, but this only shows the FPS in a specific scenario and also involves other factors like CPU and RAM. It's like saying "CPU XYZ generates X MD5 hashes per second" to measure the speed of a CPU (which is kinda how it is measured, but that's not the question)