John Siracusa dishes out some excellent advice for calibrating your TV to avoid using non-native resolutions:
You paid for all 1920×1080 pixels of your fancy new HDTV—use them! Most HDTVs have a setting somewhere to correct this problem. It may be called “Overscan,” “1:1 Pixel Mapping,” or something even more generic like “Size 1” or “Size 2.” Consult your TV’s manual to find out. (If you can’t find your paper manual, a Google search for your TV’s model number followed by “manual PDF” will usually lead to an online version.) Don’t give up; the setting is almost always there somewhere.
I recently purchased a new HDTV and noticed that many PS3 games were scaling just outside of the visible area unless I made a quick correction to it within the game’s settings. Effectively, the display is scaled to slightly less than the native resolution, meaning the picture is not as crisp as it could – or should – be.
After following John’s advice, I’ve found a setting buried within the TV’s menu called “Picture Zoom” that was set to auto. Disabling this instantly made the picture better, removing overscan entirely.