The actual PAL / SECAM resolution is 720 x 576 pixels, for 4/3 like 16/9. If the source outputs an interlaced picture a.k.a. half frames, we are talking about a resolution of 576i (i for interlaced), against 576p for a progressive signal, in full frames. At 576p its 415 Kpixels that will be displayed simultaneously. Half only: 207 Kpixels at 576i (interlaced).
NTSC works with a bigger number of pictures per seconds, 30 instead of 25, but with a smaller resolution: 538 x 480 pixels in 4/3, 720 x 480 in 16/9. The 480p of movies include “at best/max” 346 Kpixels.
Jumping to HD is in fact nothing else than improving the picture definition. 4 HD modes already exist and you can get an overview of them through the following presentation like a movie trailer on Apple’s Site or demonstration movies on Microsoft’s Site.
If it goes, here is how it would look on a QuickTime HD movie trailer :
(Here you can get an idea of the original picture and the definition improvement)

Here are 3 screenshots without any resizing of the above pictures in 480p/720p/1080p

| 480p | 720p | 1080p |
These screenshots do not represent the real quality that will be displayed.
In fact, those pictures will be processed and up-scaled or down-scaled in order to match different displays: big screen, small screen, projector…
1080p a.k.a. FULL HD is the ultimate picture quality you can get from a HDMI source such as HD-DVD player, Blu-Ray player, Playstation 3, Xbox360 HDMI
You may think..
“No problem I have a display which can support 720p or 1080p”.
“I have no HD TV, but I can still hook up my PS3 to my RGB monitor”
If that’s your case, you just forgot a small detail, the name is HDCP.
Even if your CRT monitor, LCD display, Plasma display, Projector is technically able to display 1280×720 or 1920×1080 picture resolution you won’t be able to display ANYTHING in such resolutions, BLACK SCREEN.
If you purchased a Playstation 3, X360 Elite, HD-DVD player, Blu-ray player, SAT&Cable HDTV channels set-top-box, you won’t be able to display anything in 720p or 1080p on your “old” display because it’s not HDCP compliant.
You have 3 choices:
“Hollywood’s plans for Blu-Ray and HD-DVD (HDMI/HDCP) are an outrageous attack on your freedom. Business conspiracies to restrict technology should be illegal.”