HD-DVD/Blu-Ray: both support a bunch of resolutions, but I think most will be 1920x1080 (but otherwise they support 1280x720 and other resolutions)
DVD: 720x480 is the standard resolution for DVD video
Widescreen: No standard that I know of, but common ratios are 1.85:1 and 1.66:1.
Fullscreen: a 4:3 resolution
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