>go to Compressor and make "Best Quality" DVDs which makes the files MPEG-2s which seem to me like they lower the quality of the video quite a bit.
There are two things happening during the compression process that will, indeed, affect the quality.
#1 DVD is standard definition only. So your high resolution HD video will be reduced to 720x480 pixels (standard def NTSC). If you want to deliver HD content on optical disc, as ToddNashville already stated, you'll need to create a Blu-ray disc ... and they will not play in DVD players. You can also make an HD DVD, but that format was abandoned a few years ago and hardly anyone owns one of the few HD DVD players that were ever manufactured. HD DVDs will not play in DVD players, but they will play in most later model Macs.
#2 In order for DVDs to be compatible with DVD players, the video must be compressed to MPEG-2. MPEG-2 is a long GOP (Group of Pictures) format that throws away a lot of information in order to reduce the file size and data rate. Only one in every fifteen frames contains the full video information. The remain 14 frames of each GOP only contain information that changed from the full frame. It's actually quite a bit more complicated than that, but that's a very basic and limited description.
>is there any way or any DVD authoring program besides iDVD that will accept higher quality codecs like MOV?
MOV isn't a codec; it's a audio/video container file type. A QuickTime .MOV file could be made from any number of codecs and quality levels.
The best way to maintain quality is to start with high quality to begin with; good lighting, good lens and do not record or edit in a highly compressed format like H.264 or AVCHD and especially HDV. You cannot/should not expect "Hollywood" quality when you start with a consumer, prosumer or low-end professional camera.
-DH