Those rankings are based Passmark scores which is a synthetic test. It's better than nothing, but it is be inaccurate when actual game performance is concerned.
See below link for what I used to determine that the HD 6650 is better than the GT 540M. Scroll down for the game benchmarks.
http/www.notebookcheck.net/AMD-Radeon-HD-6650M.43962.0.html
However, you must take those ranking with a grain of salt. Benchmarking laptop video card performance is not as easy as benchmarking desktop video cards. Benchmarking desktop video cards is easy because all you need to do is build a computer, then swap in/out different video cards to do the test. The only thing that changes would be the video card and the drivers (AMD / nVidia) so it is pretty much cut and dry if you are trying to determine if AMD Radeon HD 6950 is better or worse than a nVidia GTX 560.
Laptop video card performance is tricky 'cause you cannot simply have a single laptop and swap in and out various different cards. You may be testing a Mobility Radeon HD 6650 in a notebook with an AMD Phenom II dual core CPU vs. a nvidia GT 540M in a laptop with an Intel Core i5 dual core CPU.