It's a bit more complicated than that...
only material that was originally either shot on film or recorded digitally at 24 frames per second (fps) can be transcribed onto Blu-ray or HD DVD at 24fps. Everything else is usually transmitted at almost the same frequency as your local mains electricity.
Anything 'shot' originally at 24fps is transferred onto HD with the audio speeded up by about 4% and the frames rejigged to keep it in sync on a 50/60hz set..
Also not all blu-ray/hd dvd discs have the highest res material on them, in the UK btw not all HD sources (Sky HD/Virgin) transmit in 1080i all of the the time, so unless you are going to get a blu-ray or hd dvd player, a 1080i/p set could be a waste of dosh.
A SD DVD can look surprisingly good when upscaled.
Oh, be very careful if you are thinking of buying a LG (or any other) TV that has a '1080p' input label on the front, all this means is that it can display 1080p stuff at 768, which is quite cheeky eh?
And if you are thinking of buying a current blu-ray or hd dvd player, make sure it can have its' firmware upgraded (yes the standards are still evolving), otherwise you may have a very expensive book-end in a few years time!
And for the cynics, no-one is saying you need to buy anything, so why the vitriol?