DVD's are in native 480i resolution (interlaced) so it has to be upconverted by either your DVD player (if you have a progressive scan DVD) or by your projector. The process of deinterlacing and recoded the DVD contents into a progressive 480p format is not a perfect - the poorer the orginal content, the worse the output. Home videos burned on DVD at 480i come out looking very bad in the upconversion process. By contrast, inHD and DiscHD are transmitted in native 1080i - no upconversion is necessary.

Next best step - Blu-Ray or HD-DVD.