Unless you're buying a card for CloD ONLY and no other games at all, then maybe you could get that specific.
Otherwise, I'd just go on a site like
www.anandtech.com and read their card reviews/roundups. They get pretty in depth on the cards and run a boatload of tests to show you the card performance in a large variety of games/situations. And not just games too. That's where I go to make my graphics card decisions.