The answer is, it depends.
It depends on the graphic card: Gaming is 90% about the performance of the video card (GPU). As long as you have adequate RAM and a reasonably modern CPU, then the video card Graphic Processing Unit will be the determining factor in game play frame rates. Check the requirements of the individual game with the publisher, but remember that a machine with the minimum requirements will not provide very good game play.
It depends on the settings: Game settings have a lot to do with how much demand is placed on the video card. The screen resolution and the quality settings (AA, AF) can affect the frame rates. if you are not getting smooth game play, then reduce the resolution and/or the quality settings until the game is playable.
It depends on the game: Game performance also varies considerably between different games, some are more demanding than others. Research your favorite games in online forums to see what people are using for graphics.
This site has benchmarks for many current video cards with a variety of different games at different settings. You can choose the specific game, or some averaged scores
http://www.tomshardware.com/charts/2012-vga-gpgpu/benchmarks,135.html
This site rates hundreds of video cards old and new with an averaging benchmark
http://www.videocardbenchmark.net/high_end_gpus.html
The site systermrequirementslab.com has a calculator to check the requirements for many different games against your current system (Warning, this runs a Java application on your machine, you need to decide if you want to permit this. We do not endorse or verify this site for reliability.)
All else being equal, a card with a higher graphic core clock speed will perform faster than a lower clock speed of the same GPU chip, and a card with more Graphic memory (2 GB) will perform better with high demand games or higher resolution. The type of graphic memory on the card plays a small role in overall performance (DDR3 vs the faster GDDR5)
If you have a desktop machine, you can consider upgrading the video card, read this article.
You also want to make sure your machine is running as fast as it can. Don’t run other programs in the background while you are gaming, and if you are online gaming, don’t run other Internet processes like downloading or updating or email while you are gaming.
A benchmark chart of gaming performance for notebook computers is here
http://www.notebookcheck.net/Mobile-Graphics-Cards-Benchmark-List.844.0.html
Frame rates of specific games on notebooks
http://www.notebookcheck.net/Computer-Games-on-Laptop-Graphic-Cards.13849.0.html
Notebooks are a special case. Most notebooks are not capable of adequate game play on modern 3D games. And because the GPU is not capable of being upgraded in 99.9% of laptops, your existing laptop cannot be improved. If you are looking for a new gaming laptop, read this article.