The problem here is going to be your television set. The entire North American NTSC DVD distribution will be identical in quality. It's not like videotape where there can be differences between tapes. DVDs are completely digital and the image will be consistent no matter what batch they come from. A theater with a bigger screen and dark interior will make a major difference, as will the brightness and contrast settings on your television set. You will pick up more detail in a darkened room. Additionally, the sharpness of the image will depend on the quality of your TV, the cable between the DVD player and the TV set, and sometimes the quality of the DVD player itself (because of filters built into the player).
In general an HDTV-capable set will render the best picture if you have a player with composite video out and have the right cables for that.
Many computer monitors are set to render images darker than usual because they are intended more for text than movie watching, so people who watch the DVD on their computer may find the image sharper, but still dark.
In the end, the majority of differences here are because of the TV set and its settings.