OK, let me refine my statement...I cannot remember one DVD that I watched on the 4K sets that didn't annoy me because of the PQ. Never had an issue with BDs. I had a reason for throwing out all our DVDs, bins and bins of DVDs some not even opened. I threw out the whole Soprano's DVD set unopened.
Hold on a second.... the best possible resolution for DVDs is 480i, or standard definition. At the time of the format's release (1997), most people had just 4:3 Standard Definition sets (and CRTs at that), with the format being at least forward looking in that it supported 16:9 format. Some early DVD releases, however, were authored to only 4:3 even if it was a widescreen release. HDTVs didn't even start to be released until 1998, and were very expensive at that. Compare that to
this 2015 report where at least 81% of households have at least one HDTV. Also, the ideal maximized size for a Standard Definition set was 25" in the household, partially because of cost of manufacturing and such (remember, CRT). Most material produced for television prior to 2000 (at least) was made for 4:3 Standard Definition. If the original material is videotaped (e.g.
Golden Girls,
All In The Family), then there is zero possibility upscaling. If the material was filmed, then there is a possibility of a higher resolution release
provided the original source material exists.
Star Trek: The Next Generation,
Star Trek: Deep Space Nine,
Star Trek: Voyager, and
Babylon 5 are problematic in that the series was filmed, and then post-production, including the visual effects, were done on videotape. Paramount was able to re-do the effects for
ST:TNG, but that was around the time that streaming came into favor. With the exception of the original
Doctor Who story
Spearhead From Space (which was 100% filmed due to a strike at the time), most of the
Doctor Who stories (as well as BBC Britcoms) were hybrid in that they combined both videotaped interior scenes as well as filmed exterior scenes, with select Doctor Who stories prior to 1986 and all Doctor Who stories from 1986 to the original series conclusion in 1989 being on videotape.
In comparison, the maximum resolution for a BluRay disc is 1080p, and a UltraHD is up to 4K. Much higher resolution available.
There are some tricks available. I know that the program
Handbrake has the ability to de-interlace a interlaced source, which does somewhat improve the picture. But that only goes so far. The best I've seen in releases is upconversion from 480i to 720p, with some mixed results. Because the physical media market has imploded, some less-well known won't see a BluRay release. I'm not holding my breath for a BluRay re-release of
Emergency! .