HDMI is an interface that holds (standard 1920X1080) digital audio and video transmission and VGA is an interface for analog video (standard 640X480).
The resolution you wanted 1080 (1920X080) from your d-sub input. If your system can handle WXUGA which is 1920X1200, then it's more than the HDMI standard 1080 of resolutions.
However, DVD unless your player is upscaled, it can only support 480 NTSC or up to 625 for PAL.