The DVD version was the 16:9 transfer.
The original was shot on Super35 film, with framing for 4:3 and 16:9, but the CGI was only rendered for 4:3 (and 480i), since even that was pushing the technology available in the day. The belief was that eventually the CGI could be re-rendered at 16:9 (and potentially higher resolution), but then Warner Brothers lost the files and the composite scene source elements. So for the 16:9 transfer, live-action only scenes were re-framed (as originally intended so look okay), but pure-CGI and composite live+CGI scenes were cropped and zoomed to fill the screen, looking blurry at best (and in some composite scenes, very badly framed).
Also, WB didn't take good care of the original film, so some was scratched and dirty, leaving some scenes (especially early in season 1) looking snowy.
With some renewed B5 interest, there was a Blu-Ray release a couple of years ago. It's the 4:3 original, with cleanup of the quality. It's much better than the DVD release. What I see on Youtube appears to be the Blu-Ray edition, with 4:3 content at 1080p, except for the pilot "The Gathering", which is the TNT "special edition" (in addition to getting the 16:9 treatment, it also has a few story edits, which is why that's generally the "preferred" edition even with quality issues).