You'll may find that your graphics card, under Linux, was using the open source drivers. Unfortunately in most circumstances these yield poor results as they're not using the full capacity of the card, due to lack of specifications and communication from the manufacturers.
In a lot of cases you can use the proprietory drivers to run the graphics card, but that may cause other issues in itself. If you're using a decent card and getting crap performance, you may wish to look into this. Using them often differs from distro to distro, unfortunately.