Are you sure on the 720? I didn't look it up but i thought 480p was the best dvd resolution on disk. The older dvd players were 480i output, then the later ones had 480p outputs such as component or dvi or hdmi. Sometimes it is better to let the player do the upscaling, other times it's better to let the tv do the job. If you really want to see good hdtv, get an over the air box. They pull in the signal with the full 19mhz bandwith, 3 of the local stations here are 720p and the other is 1080i, no compression on over the air channels unless they are pushing 2 or 3 channels in the bandwith. All satellite hd or cable hd is compressed.
480p is the best you will see from regular dvd player no matter what they are selling it as. Blue ray will do up to 1080p.
"Although many resolutions and formats are supported, most consumer DVD-Video discs use either 4:3 or anamorphic 16:9 aspect ratio MPEG-2 video, stored at a resolution of 720×480 (NTSC) "
720 is the width 480 is the height(how many lines are squeezed into the picture. 480i does 1 lines, then skips one, then does line 3, then line 5, when its done, it goes back to the top and does the even numbered lines 2,4,6. 480p does them all in sequence. From what i have heard, you need a really big tv to see the difference between 1080i and 1080p. Then there is the refresh or scan rate which can be 60hz or 120hz higher the better. Find the tv size you like and i can bet you the 120hz version cost quite a bit more than the older style 60hz. Me, i have a old 30" 16x9 sony hdtv crt with no digital tuner but boy does it have a nice picture with 720p or 1080i.