LED just defines the backlight type, it replaces an older style of backlighting, some people prefer LED backlighting but it is not for me.
Could be lots of problems in all honest causing the issue you describe, does your set have a 100hz mode or something similar ? Try turning that on, it can sometimes make a world of difference. Like the post above says, it will depend on the source, try feeding it a bit of bluray or something along those lines, the issue might not be as prevalent.
You find standard def always looks pretty rubbish on big sets especially LCD sets. With something like 720p or 1080p you are going to get much better results.