Is there a noticeable difference between Blu-ray and regular DVDs?

[Gogogodzilla]

Using a regular television or even a 720 High Definition television.

[AdolfHitler]

yes very big

[GrumpyMac]

"Is there a noticeable difference between HD and standard def?"

You wont see much difference on a standard def TV. But in general - high def picture quality is clearly better on a HDTV.

Standard def - will play on your grandmothers black and white TV from the 1950's. HDTV takes advantage of seventy years of advancement.