I study video engineering let me clear some stuff up.
NTSC is 720 x 480 interlaced frames at 60Hz, This framterate was picked because the AC power in the US cycles at 60Hz. The pixels on an NTSC TV are not square like the ones on your computer monitor. They are slightly skinny, widescreen TV is the same, but the pixels are simply wider than they are tall
PAL, on the other hand is 525 lines, but at 50Hz, a ower framerate, again, because the UK and Europe AC power cycles at 50 Hz. PAL uses a very interesting solution for widescreen broadcast. They use a system called PAL Plus, in which widescreen content is broadcasted letterboxed, BUT with extra data in the space that the letterboxes use, thus when a PAL Plus receiver is used, the box will take that data to fill in the information that would otherwise be lost in the cropping procedure. This system is not as widely used anymore as it once was, however.
I'm not going to go into SECAM, because nobody uses it anymore.